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Allow or block email using the Tenant Allow/Block List

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In Microsoft 365 organizations with mailboxes in Exchange Online or standalone Exchange Online Protection (EOP) organizations without Exchange Online mailboxes, admins can create and manage entries for domains and email addresses (including spoofed senders) in the Tenant Allow/Block List. For more information about the Tenant Allow/Block List, see Manage allows and blocks in the Tenant Allow/Block List.

This article describes how admins can manage entries for email senders in the Microsoft Defender portal and in Exchange Online PowerShell.

What do you need to know before you begin?

  • You open the Microsoft Defender portal at https://security.microsoft.com. To go directly to the Tenant Allow/Block Lists page, use https://security.microsoft.com/tenantAllowBlockList. To go directly to the Submissions page, use https://security.microsoft.com/reportsubmission.

  • To connect to Exchange Online PowerShell, see Connect to Exchange Online PowerShell. To connect to standalone EOP PowerShell, see Connect to Exchange Online Protection PowerShell.

  • Entry limits for domains and email addresses:

    • Exchange Online Protection: The maximum number of allow entries is 500, and the maximum number of block entries is 500 (1000 domain and email address entries in total).
    • Defender for Office 365 Plan 1: The maximum number of allow entries is 1000, and the maximum number of block entries is 1000 (2000 domain and email address entries in total).
    • Defender for Office 365 Plan 2: The maximum number of allow entries is 5000, and the maximum number of block entries is 10000 (15000 domain and email address entries in total).

  • For spoofed senders, the maximum number of allow entries and block entries is 1024 (1024 allow entries and no block entries, 512 allow entries and 512 block entries, etc.).

  • Entries for spoofed senders never expire.

  • For blocking inbound and outbound email from a domain, any subdomains in that domain, and any email addresses in that domain, create the block entry using the syntax: *.TLD, where TLD can be any top-level domain, internal domain, or email address domain.

  • For blocking inbound and outbound email from a sudomain in a domain and any email addresses in that subdomain, create the block entry using the syntax: *.SD1.TLD, *.SD2.SD1.TLD, *.SD3.SD2.SD1.TLD, etc. for internal domains and email address domains.

  • For details about the syntax for spoofed sender entries, see the Domain pair syntax for spoofed sender entries section later in this article.

  • An entry should be active within 5 minutes.

  • You need to be assigned permissions before you can do the procedures in this article. You have the following options:

    • Microsoft Defender XDR Unified role based access control (RBAC) (If Email & collaboration > Defender for Office 365 permissions is Active. Affects the Defender portal only, not PowerShell): Authorization and settings/Security settings/Detection tuning (manage) or Authorization and settings/Security settings/Core security settings (read).

    • Exchange Online permissions:

      • Add and remove entries from the Tenant Allow/Block List: Membership in one of the following role groups:
        • Organization Management or Security Administrator (Security admin role).
        • Security Operator (Tenant AllowBlockList Manager).
      • Read-only access to the Tenant Allow/Block List: Membership in one of the following role groups:
        • Global Reader
        • Security Reader
        • View-Only Configuration
        • View-Only Organization Management

    • Microsoft Entra permissions: Membership in the Global Administrator*, Security Administrator, Global Reader, or Security Reader roles gives users the required permissions and permissions for other features in Microsoft 365.

      Important

      * Microsoft recommends that you use roles with the fewest permissions. Using lower permissioned accounts helps improve security for your organization. Global Administrator is a highly privileged role that should be limited to emergency scenarios when you can't use an existing role.

Domains and email addresses in the Tenant Allow/Block List

Create allow entries for domains and email addresses

You can't create allow entries for domains and email addresses directly in the Tenant Allow/Block List. Unnecessary allow entries expose your organization to malicious email that would have been filtered by the system.

Instead, you use the Emails tab on the Submissions page at https://security.microsoft.com/reportsubmission?viewid=email. When you submit a blocked message as I've confirmed it's clean and then select Allow this message, an allow entry for the sender is added to the Domains & email addresses tab on the Tenant Allow/Block Lists page. For instructions, see Submit good email to Microsoft.

Tip

Allow entries from submissions are added during mail flow based on the filters that determined the message was malicious. For example, if the sender email address and a URL in the message are determined to be malicious, an allow entry is created for the sender (email address or domain) and the URL.

During mail flow or time of click, if messages containing the entities in the allow entries pass other checks in the filtering stack, the messages are delivered (all filters associated with the allowed entities are skipped). For example, if a message passes email authentication checks, URL filtering, and file filtering, a message from an allowed sender email address is delivered if it's also from an allowed sender.

By default, allow entries for domains and email addresses, files, and URLs are kept for 45 days after the filtering system determines that the entity is clean, and then the allow entry is removed. Or you can set allow entries to expire up to 30 days after you create them. Allow entries for spoofed senders never expire.

Create block entries for domains and email addresses

To create block entries for domains and email addresses, use either of the following methods:

  • From the Emails tab on the Submissions page at https://security.microsoft.com/reportsubmission?viewid=email. When you submit a message as I've confirmed it's a threat, you can select Block all emails from this sender or domain to add a block entry to the Domains & email addresses tab on the Tenant Allow/Block Lists page. For instructions, see Report questionable email to Microsoft.

  • From the Domains & addresses tab on the Tenant Allow/Block Lists page or in PowerShell as described in this section.

To create block entries for spoofed senders, see this section later in this article.

Email from these blocked senders is marked as high confidence phishing and quarantined.

Note

Currently, subdomains of the specified domain aren't blocked. For example, if you create a block entry for email from contoso.com, mail from marketing.contoso.com isn't also blocked. You need to create a separate block entry for marketing.contoso.com.

Users in the organization also can't send email to these blocked domains and addresses. The message is returned in the following non-delivery report (also known as an NDR or bounce message): 550 5.7.703 Your message can't be delivered because messages to XXX, YYY are blocked by your organization using Tenant Allow Block List. The entire message is blocked for all internal and external recipients of the message, even if only one recipient email address or domain is defined in a block entry.

Use the Microsoft Defender portal to create block entries for domains and email addresses in the Tenant Allow/Block List

  1. In the Microsoft Defender portal at https://security.microsoft.com, go to Policies & rules > Threat Policies > Rules section > Tenant Allow/Block Lists. Or, to go directly to the Tenant Allow/Block Lists page, use https://security.microsoft.com/tenantAllowBlockList.

  2. On the Tenant Allow/Block Lists page, verify that the Domains & addresses tab is selected.

  3. On the Domains & addresses tab, select Block.

  4. In the Block domains & addresses flyout that opens, configure the following settings:

    • Domains & addresses: Enter one email address or domain per line, up to a maximum of 20.

    • Remove block entry after: Select from the following values:

      • 1 day
      • 7 days
      • 30 days (default)
      • Never expire
      • Specific date: The maximum value is 90 days from today.

    • Optional note: Enter descriptive text for why you're blocking the email addresses or domains.

  5. When you're finished in the Block domains & addresses flyout, select Add.

Back on the Domains & email addresses tab, the entry is listed.

Use PowerShell to create block entries for domains and email addresses in the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

New-TenantAllowBlockListItems -ListType Sender -Block -Entries "DomainOrEmailAddress1","DomainOrEmailAddress1",..."DomainOrEmailAddressN" <-ExpirationDate Date | -NoExpiration> [-Notes <String>]

This example adds a block entry for the specified email address that expires on a specific date.

New-TenantAllowBlockListItems -ListType Sender -Block -Entries "test@badattackerdomain.com","test2@anotherattackerdomain.com" -ExpirationDate 8/20/2022

For detailed syntax and parameter information, see New-TenantAllowBlockListItems.

Use the Microsoft Defender portal to view entries for domains and email addresses in the Tenant Allow/Block List

In the Microsoft Defender portal at https://security.microsoft.com, go to Policies & rules > Threat Policies > Tenant Allow/Block Lists in the Rules section. Or, to go directly to the Tenant Allow/Block Lists page, use https://security.microsoft.com/tenantAllowBlockList.

Verify the Domains & addresses tab is selected.

On the Domains & addresses tab, you can sort the entries by clicking on an available column header. The following columns are available:

  • Value: The domain or email address.
  • Action: The value Allow or Block.
  • Modified by
  • Last updated
  • Last used date: The date the entry was last used in the filtering system to override the verdict.
  • Remove on: The expiration date.
  • Notes

To filter the entries, select Filter. The following filters are available in the Filter flyout that opens:

  • Action: The values are Allow and Block.
  • Never expire: or
  • Last updated: Select From and To dates.
  • Last used date: Select From and To dates.
  • Remove on: Select From and To dates.

When you're finished in the Filter flyout, select Apply. To clear the filters, select Clear filters.

Use the Search box and a corresponding value to find specific entries.

To group the entries, select Group and then select Action. To ungroup the entries, select None.

Use PowerShell to view entries for domains and email addresses in the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

Get-TenantAllowBlockListItems -ListType Sender [-Allow] [-Block] [-Entry <Domain or Email address value>] [<-ExpirationDate Date | -NoExpiration>]

This example returns all allow and block entries for domains and email addresses.

Get-TenantAllowBlockListItems -ListType Sender

This example filters the results for block entries for domains and email addresses.

Get-TenantAllowBlockListItems -ListType Sender -Block

For detailed syntax and parameter information, see Get-TenantAllowBlockListItems.

Use the Microsoft Defender portal to modify entries for domains and email addresses in the Tenant Allow/Block List

In existing domain and email address entries, you can change the expiration date and note.

  1. In the Microsoft Defender portal at https://security.microsoft.com, go to Policies & rules > Threat Policies > Rules section > Tenant Allow/Block Lists. Or, to go directly to the Tenant Allow/Block Lists page, use https://security.microsoft.com/tenantAllowBlockList.

  2. Verify the Domains & addresses tab is selected.

  3. On the Domains & addresses tab, select the entry from the list by selecting the check box next to the first column, and then select the Edit action that appears.

  4. In the Edit domains & addresses flyout that opens, the following settings are available:

    • Block entries:
      • Remove block entry after: Select from the following values:
        • 1 day
        • 7 days
        • 30 days
        • Never expire
        • Specific date: The maximum value is 90 days from today.
      • Optional note
    • Allow entries:
      • Remove allow entry after: Select from the following values:
        • 1 day
        • 7 days
        • 30 days
        • 45 days after last used date
        • Specific date: The maximum value is 30 days from today.
      • Optional note

    When you're finished in the Edit domains & addresses flyout, select Save.

Tip

In the details flyout of an entry on the Domains & addresses tab, use View submission at the top of the flyout to go to the details of the corresponding entry on the Submissions page. This action is available if a submission was responsible for creating the entry in the Tenant Allow/Block List.

Use PowerShell to modify entries for domains and email addresses in the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

Set-TenantAllowBlockListItems -ListType Sender <-Ids <Identity value> | -Entries <Value>> [<-ExpirationDate Date | -NoExpiration>] [-Notes <String>]

This example changes the expiration date of the specified block entry for the sender email address.

Set-TenantAllowBlockListItems -ListType Sender -Entries "julia@fabrikam.com" -ExpirationDate "9/1/2022"

For detailed syntax and parameter information, see Set-TenantAllowBlockListItems.

Use the Microsoft Defender portal to remove entries for domains and email addresses from the Tenant Allow/Block List

  1. In the Microsoft Defender portal at https://security.microsoft.com, go to Policies & rules > Threat Policies > Rules section > Tenant Allow/Block Lists. Or, to go directly to the Tenant Allow/Block Lists page, use https://security.microsoft.com/tenantAllowBlockList.

  2. Verify the Domains & addresses tab is selected.

  3. On Domains & addresses tab, do one of the following steps:

    • Select the entry from the list by selecting the check box next to the first column, and then select the Delete action that appears.

    • Select the entry from the list by clicking anywhere in the row other than the check box. In the details flyout that opens, select Delete at the top of the flyout.

      Tip

      • To see details about other entries without leaving the details flyout, use Previous item and Next item at the top of the flyout.
      • You can select multiple entries by selecting each check box, or select all entries by selecting the check box next to the Value column header.

  4. In the warning dialog that opens, select Delete.

Back on the Domains & addresses tab, the entry is no longer listed.

Use PowerShell to remove entries for domains and email addresses from the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

Remove-TenantAllowBlockListItems -ListType Sender `<-Ids <Identity value> | -Entries <Value>>

This example removes the specified entry for domains and email addresses from the Tenant Allow/Block List.

Remove-TenantAllowBlockListItems -ListType Sender -Entries "adatum.com"

For detailed syntax and parameter information, see Remove-TenantAllowBlockListItems.

Spoofed senders in the Tenant Allow/Block List

When you override the verdict in the spoof intelligence insight, the spoofed sender becomes a manual allow or block entry that only appears on the Spoofed senders tab on the Tenant Allow/Block Lists page.

Create allow entries for spoofed senders

To create allow entries for spoofed senders, use any of the following methods:

Note

Allow entries for spoofed senders account for intra-org, cross-org, and DMARC spoofing.

Only the combination of the spoofed user and the sending infrastructure as defined in the domain pair is allowed to spoof.

Allow entries for spoofed senders never expire.

Use the Microsoft Defender portal to create allow entries for spoofed senders in the Tenant Allow/Block List

In the Tenant Allow/Block List, you can create allow entries for spoofed senders before they're detected and blocked by spoof intelligence.

  1. In the Microsoft Defender portal at https://security.microsoft.com, go to Policies & rules > Threat Policies > Rules section > Tenant Allow/Block Lists. Or, to go directly to the Tenant Allow/Block Lists page, use https://security.microsoft.com/tenantAllowBlockList.

  2. On the Tenant Allow/Block Lists page, select the Spoofed senders tab.

  3. On the Spoofed senders tab, select Add.

  4. In the Add new domain pairs flyout that opens, configure the following settings:

    • Add domain pairs with wildcards: Enter domain pair per line, up to a maximum of 20. For details about the syntax for spoofed sender entries, see the Domain pair syntax for spoofed sender entries section later in this article.

    • Spoof type: Select one of the following values:

      • Internal: The spoofed sender is in a domain that belongs to your organization (an accepted domain).
      • External: The spoofed sender is in an external domain.

    • Action: Select Allow or Block.

    When you're finished in the Add new domain pairs flyout, select Add.

Back on the Spoofed senders tab, the entry is listed.

Use PowerShell to create allow entries for spoofed senders in the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

New-TenantAllowBlockListSpoofItems -Identity Default -Action Allow -SpoofedUser <Domain | EmailAddress> -SendingInfrastructure <Domain | IPAddress/24> -SpoofType <External | Internal>

This example creates an allow entry for the sender bob@contoso.com from the source contoso.com.

New-TenantAllowBlockListSpoofItems -Identity Default -Action Allow -SendingInfrastructure contoso.com -SpoofedUser bob@contoso.com -SpoofType External

For detailed syntax and parameter information, see New-TenantAllowBlockListSpoofItems.

Create block entries for spoofed senders

To create block entries for spoofed senders, use any of the following methods:

Note

Only the combination of the spoofed user and the sending infrastructure defined in the domain pair is blocked from spoofing.

Email from these senders is marked as phishing. What happens to the messages is determined by the anti-spam policy that detected the message for the recipient. For more information, see the Phishing detection action in EOP anti-spam policy settings.

When you configure a block entry for a domain pair, the spoofed sender becomes a manual block entry that appears only on the Spoofed senders tab in the Tenant Allow/Block List.

Block entries for spoofed senders never expire.

Use the Microsoft Defender portal to create block entries for spoofed senders in the Tenant Allow/Block List

The steps are nearly identical to creating allow entries for spoofed senders as previously described in this article.

The only difference is: for the Action value in Step 4, select Block instead of Allow.

Use PowerShell to create block entries for spoofed senders in the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

New-TenantAllowBlockListSpoofItems -Identity Default -Action Block -SpoofedUser <Domain | EmailAddress> -SendingInfrastructure <Domain | IPAddress/24> -SpoofType <External | Internal>

This example creates a block entry for the sender laura@adatum.com from the source 172.17.17.17/24.

New-TenantAllowBlockListSpoofItems -Identity Default -Action Block -SendingInfrastructure 172.17.17.17/24 -SpoofedUser laura@adatum.com -SpoofType External

For detailed syntax and parameter information, see New-TenantAllowBlockListSpoofItems.

Use the Microsoft Defender portal to view entries for spoofed senders in the Tenant Allow/Block List

In the Microsoft Defender portal at https://security.microsoft.com, go to Policies & rules > Threat Policies > Tenant Allow/Block Lists in the Rules section. Or, to go directly to the Tenant Allow/Block Lists page, use https://security.microsoft.com/tenantAllowBlockList.

Verify the Spoofed senders tab is selected.

On the Spoofed senders tab, you can sort the entries by clicking on an available column header. The following columns are available:

  • Spoofed user
  • Sending infrastructure
  • Spoof type: The available values are Internal or External.
  • Action: The available values are Block or Allow.

To filter the entries, select Filter. The following filters are available in the Filter flyout that opens:

  • Action: The available values are Allow and Block.
  • Spoof type: The available values are Internal and External.

When you're finished in the Filter flyout, select Apply. To clear the filters, select Clear filters.

Use the Search box and a corresponding value to find specific entries.

To group the entries, select Group and then select one of the following values:

  • Action
  • Spoof type

To ungroup the entries, select None.

Use PowerShell to view entries for spoofed senders in the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

Get-TenantAllowBlockListSpoofItems [-Action <Allow | Block>] [-SpoofType <External | Internal>

This example returns all spoofed sender entries in the Tenant Allow/Block List.

Get-TenantAllowBlockListSpoofItems

This example returns all allow spoofed sender entries that are internal.

Get-TenantAllowBlockListSpoofItems -Action Allow -SpoofType Internal

This example returns all blocked spoofed sender entries that are external.

Get-TenantAllowBlockListSpoofItems -Action Block -SpoofType External

For detailed syntax and parameter information, see Get-TenantAllowBlockListSpoofItems.

Use the Microsoft Defender portal to modify entries for spoofed senders in the Tenant Allow/Block List

When you modify an allow or block entry for spoofed senders in the Tenant Allow/Block list, you can only change the entry from Allow to Block, or vice-versa.

  1. In the Microsoft Defender portal at https://security.microsoft.com, go to Policies & rules > Threat Policies > Rules section > Tenant Allow/Block Lists. Or, to go directly to the Tenant Allow/Block Lists page, use https://security.microsoft.com/tenantAllowBlockList.

  2. Select the Spoofed senders tab.

  3. Select the entry from the list by selecting the check box next to the first column, and then select the Edit action that appears.

  4. In the Edit spoofed sender flyout that opens, select Allow or Block, and then select Save.

Use PowerShell to modify entries for spoofed senders in the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

Set-TenantAllowBlockListSpoofItems -Identity Default -Ids <Identity value> -Action <Allow | Block>

This example changes the specified spoofed sender entry from an allow entry to a block entry.

Set-TenantAllowBlockListItems -Identity Default -Ids 3429424b-781a-53c3-17f9-c0b5faa02847 -Action Block

For detailed syntax and parameter information, see Set-TenantAllowBlockListSpoofItems.

Use the Microsoft Defender portal to remove entries for spoofed senders from the Tenant Allow/Block List

  1. In the Microsoft Defender portal at https://security.microsoft.com, go to Policies & rules > Threat Policies > Rules section > Tenant Allow/Block Lists. Or, to go directly to the Tenant Allow/Block Lists page, use https://security.microsoft.com/tenantAllowBlockList.

  2. Select the Spoofed senders tab.

  3. On the Spoofed senders tab, select the entry from the list by selecting the check box next to the first column, and then select the Delete action that appears.

    Tip

    You can select multiple entries by selecting each check box, or select all entries by selecting the check box next to the Spoofed user column header.

  4. In the warning dialog that opens, select Delete.

Use PowerShell to remove entries for spoofed senders from the Tenant Allow/Block List

In Exchange Online PowerShell, use the following syntax:

Remove-TenantAllowBlockListSpoofItems -Identity domain.com\Default -Ids <Identity value>

Remove-TenantAllowBlockListSpoofItems -Identity domain.com\Default -Ids d86b3b4b-e751-a8eb-88cc-fe1e33ce3d0c

This example removes the specified spoofed sender. You get the Ids parameter value from the Identity property in the output of Get-TenantAllowBlockListSpoofItems command.

For detailed syntax and parameter information, see Remove-TenantAllowBlockListSpoofItems.

Domain pair syntax for spoofed sender entries

A domain pair for a spoofed sender in the Tenant Allow/Block List uses the following syntax: <Spoofed user>, <Sending infrastructure>.

  • Spoofed user: This value involves the email address of the spoofed user that's displayed in the From box in email clients. This address is also known as the 5322.From or P2 sender address. Valid values include:

    • An individual email address (for example, chris@contoso.com).
    • An email domain (for example, contoso.com).
    • The wildcard character (*).

  • Sending infrastructure: This value indicates the source of messages from the spoofed user. Valid values include:

    • The domain found in a reverse DNS lookup (PTR record) of the source email server's IP address (for example, fabrikam.com).
    • If the source IP address has no PTR record, then the sending infrastructure is identified as <source IP>/24 (for example, 192.168.100.100/24).
    • A verified DKIM domain.
    • The wildcard character (*).

Here are some examples of valid domain pairs to identify spoofed senders:

  • contoso.com, 192.168.100.100/24
  • chris@contoso.com, fabrikam.com
  • *, contoso.net

Note

You can specify wildcards in the sending infrastructure or in the spoofed user, but not in both at the same time. For example, *, * isn't permitted.

If you're using a domain instead of the IP address or IP address range in the sending infrastructure, the domain needs to match the PTR record for the connecting IP in the Authentication-Results header. You can determine the PTR by running the command: ping -a <IP address>. We also recommend using the PTR Organization Domain as the domain value. For example, if the PTR resolves to "smtp.inbound.contoso.com", you should use "contoso.com" as the sending infrastructure.

Adding a domain pair allows or blocks the combination of the spoofed user and the sending infrastructure only. For example, you add an allow entry for the following domain pair:

  • Domain: gmail.com
  • Sending infrastructure: tms.mx.com

Only messages from that domain and sending infrastructure pair are allowed to spoof. Other senders attempting to spoof gmail.com aren't allowed. Messages from senders in other domains originating from tms.mx.com are checked by spoof intelligence.

About impersonated domains or senders

You can't create allow entries in the Tenant Allow/Block List for messages that were detected as impersonated users or impersonated domains by anti-phishing policies in Defender for Office 365.

Submitting a message that was incorrectly blocked as impersonation on the Emails tab of the Submissions page at https://security.microsoft.com/reportsubmission?viewid=email doesn't add the sender or domain as an allow entry in the Tenant Allow/Block List.

Instead, the domain or sender is added to the Trusted senders and domains section in the anti-phishing policy that detected the message.

For submission instructions for impersonation false positives, see Report good email to Microsoft.

Note

Currently, User (or graph) Impersonation isn't taken care of from here.