Outgoing Mail Blocked

Question

why do i keep getting messages that my outgoing mail is blocked because i exceed some unkown number of emails???

Answer 1

Hi, I'm John!

This can happen if the system detects unusual activity, or if your account hasn’t been fully verified.

Can I ask if you’re using Outlook with a personal Microsoft account or through a work/school account?

For personal accounts, the best place to start is making sure your account is fully verified, check that your security info (like your phone number or alternate email) is up to date at https://account.microsoft.com Once that’s done, the limits often lift within 24 hours.

If it’s a work or school account, you may need to reach out to your IT admin since they control sending limits for your organization.

For more detailed guidance please see "How can I increase sending limits?" section here: https://support.microsoft.com/office/sending-limits-in-outlook-com-279ee200-594c-40f0-9ec8-bb6af7735c2e

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I really hope this information is helpful! Let me know if you have any further questions or concerns.

Regards,

John J.D.

Answer 2

Outgoing mail is being blocked because the service detects that the mailbox or tenant is sending more email than allowed, often due to spam-like or bulk-sending behavior.

In Exchange Online/Outlook.com, this commonly surfaces as an NDR (bounce) with a code like 550 5.7.705 Access denied, tenant has exceeded threshold. This means:

• The system has determined that too much spam or bulk mail is being sent from the organization or account.
• Typical causes include:
  • A compromised account sending spam without the user’s knowledge.
  • A compromised on-premises server or connector routing large volumes of mail through Microsoft 365.
• When the threshold is exceeded, outgoing mail is blocked until the underlying issue is fixed and the block is removed.

Only an email admin for the tenant can clear this:

1. Investigate and fix the cause of high-volume or spam traffic, for example by following guidance such as:
   • Responding to a compromised email account.
   • Enforcing multifactor authentication.
   • Hardening the tenant’s security configuration.
2. After the root cause is addressed, contact Microsoft Support to request removal of the sending block.

If this is a personal Outlook.com account and not part of an organization, the same principle applies: the account may have been flagged for sending patterns that look like spam or bulk mail, often due to compromise. In that case, secure the account (change password, enable MFA, review rules/forwarding) and then work with Microsoft support via the error/NDR guidance to restore normal sending.

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References:

• NDR error codes 550 5.7.703, 550 5.7.705, 550 5.7.708, and 550 5.7.750