Exchange on subdomain

Question

Hi,

Currently, our organization uses the G-Suite solution to manage corporate mail on our main domain 'maindomain.com'. But due to very strict restrictions on the number of messages per day, G-Suite is not suitable for sending automated error alerts, reminders, notifications to clients, etc.

For these purposes we want to organize new subdomain 'mailgate.maindomain.com', managed by Office 365 Exchange Online. We use Office 365 Business Essentials subscription.

Our DNS records:

    @               IN      MX      1       ASPMX.L.GOOGLE.COM.

    @               IN      MX      5       ALT1.ASPMX.L.GOOGLE.COM.

    @               IN      MX      5       ALT2.ASPMX.L.GOOGLE.COM.

    @               IN      MX      10      ASPMX2.GOOGLEMAIL.COM.

    @               IN      MX      10      ASPMX3.GOOGLEMAIL.COM.

    @               IN      MX      10      ASPMX4.GOOGLEMAIL.COM.

    @               IN      MX      10      ASPMX5.GOOGLEMAIL.COM.

    mailgate        IN      MX      1       mailgate-maindomain-com.mail.protection.outlook.com

    mailgate        IN      TXT v=spf1 ip4:[xxx].[xxx].[xxx].[xxx] include:spf.protection.outlook.com ~all

    At the moment we can:

    1. Send mails from any external domains to mailgate.maindomain.com mailboxes.

    2. Send mails from maindomain.com mailboxes to mailgate.maindomain.com mailboxes.

    But via https://outlook.office365.com/owa/ we cannot send any emails from mailgate.maindomain.com neither to any external domains, nor to maindomain.com. 

    We get the following error message "The message can't be sent right now. Please try again later.",

    or 

    "Delivery has failed to these recipients or groups:

******@gmail.com

Your message wasn't delivered because the recipient's email provider rejected it.

Diagnostic information for administrators:

Generating server: CYxxx.namprd22.prod.outlook.com

******@gmail.com

Remote Server returned '550 5.7.708 Service unavailable. Access denied, traffic not accepted from this IP. For more information please go to http://go.microsoft.com/fwlink/?LinkId=526653 AS(7171) [CYxxx.namprd22.prod.outlook.com]'

"

Please let us know how to resolve this issue.

Regards,

Alex Svitoch

Answer 1

Hi Rudy,

It looks like I solved the problem with the help of this article : 

Configure Email Coexistence between Office 365 & Google Apps

Regards,

Alex Svitoch

Answer 2

To date, we have made only 20-30 attempts to send mails.

So we could not exceed the limits.

Answer 3

Please note that like Google, Exchange Online also places limits on sending of bulk mail.

Please ensure that you stay below this limit -

https://technet.microsoft.com/en-us/library/exchange-online-limits.aspx

Answer 4

Hi Alex,

Thank you for posting. When you say “But via https://outlook.office365.com/owa/ we cannot send any emails from mailgate.maindomain.com neither to any external domains, nor to maindomain.com”, may I know whether this issue happen with every mailbox or specific mailbox? 

If you are receiving this error message” Remote Server returned '550 5.7.708 Service unavailable. Access denied, traffic not accepted from this IP”, you may check whether the user mailbox/IP address are blocked. If so, as an admin you can unblock your blocked Office 365 email account via using Exchange admin center.

For more detailed information, please refer to the article: Removing a user, domain, or IP address from a block list after sending spam email

Moreover, please provide us with the detailed NDR and tenant information via the Private Message so that we can further assist you.

Your time and understanding will be highly appreciated.

Best regards,

Shyamal

Answer 5

Google is rejecting it, either because of the volume (& quality) or because of the volume and new configuration.

Does gsuite let you whitelist domains? (It may not help that, it looks like a gateway is dropping it.)

FWIW, office 365 may have issues with sending a high number of alerts and no other traffic.