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I have a Postfix installed on an Oracle Linux server. This Postfix is configured to receive emails from another Postfix server, which are sent externally through the Fortinet Cloud Email Security Gateway.

From time to time, mail delivery fails and the mail.log displays the following error message:

"Delivery temporarily suspended: Connect to abc.fortimailcloud.com[x.x.x.x]:25: connection timed out."

When attempting to issue a telnet command from the Postfix server to abc.fortimailcloud.com[x.x.x.x]:25, it also fails.

After a few minutes, the email automatically delivery starts again. This solution is used for sending bulk promotional emails. We have noticed that one of the bulk email lists includes numerous incorrect email addresses and invalid domain names.

According to the Fortinet Cloud team, they have confirmed that there are no issues on their end. Also, forti mail cloud does not check email addresses or domain validity. However, I would appreciate your support in resolving this issue. If there is no issue on the Postfix side, I need to prove it.

Diads
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  • Your mass mailings should include bounce processing. Sending bulk email with bad addresses gets servers blacklisted. – Paul Jun 08 '23 at 11:53
  • If bulk email is sent with invalid addresses, can this be a reason for the temporary server blacklist and temporary delivery suspension? – Diads Jun 18 '23 at 06:23
  • Yes, especially if the server keeps sending to the same bad addresses. Bad addresses should be removed with bounce processing. – Paul Jun 18 '23 at 10:27

2 Answers2

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You didn't mentioned how many emails you are sending, but I Assume that you might have sent large number of emails to your desired destination.

Sending a high volume of emails to a destination server can sometimes result in the emails getting queued on the source server for security reasons. This can occur if the destination server or its associated security systems detect the high volume of incoming emails as a potential spam or abuse attempt.

Zareh Kasparian
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  • Yes, that is correct. We are sending a large number of emails, which is why we are utilizing a dedicated bulk mail gateway (destination server). This server is specifically designed to handle high volumes of incoming emails, it does not mistakenly detect or block the high volume as spam. Anyway, I need to clarify the postfix end. Is there a way to check and confirm the postfix side? – Diads Jun 18 '23 at 06:12
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Yes, that is correct. We are sending a large number of emails, which is why we are utilizing a dedicated bulk mail gateway (destination server). This server is specifically designed to handle high volumes of incoming emails, it does not mistakenly detect or block the high volume as spam. Anyway, I need to clarify the postfix end. Is there a way to check and confirm the postfix side?

Diads
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