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Welcome to Cisco Support Community. We would love to have your feedback.

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New Member

Fixup Protocol SMTP 25

Is Fixup protocol smtp 25 for inbound only? I've heard this can cause issues of all kinds. Should I disable it?


Re: Fixup Protocol SMTP 25


Please refer to following link-

This is for inbound smtp connections when outside clients are connecting to internal mail servers. Going by the link, if your mail server requires use of commands other than mentioned in the link (HELO, MAIL, RCPT, DATA, RSET, NOOP, and QUIT), you may disable the fixup. This is generally true incase of Microsoft Exchange servers which uses Extended commands.

If you face issues with mails, you may test things with disabling the same-

no fixup protocol smtp 25

Hope this helps.



New Member

Re: Fixup Protocol SMTP 25

If I am having trouble sending messages out, will disabling the fixup protocol smtp 25 have any affect?

New Member

Re: Fixup Protocol SMTP 25


Can u describe the issues sending mail out.

Is this domain specific or does it affect all outbound mail?

New Member

Re: Fixup Protocol SMTP 25

== Issue is we cannot send emails to a few internet domain i.e.

== Messages for these domains are stuck in the queue in a retry state.

New Member

Re: Fixup Protocol SMTP 25

It is not aware of inbound vs. outbound. Mailguard -- aka. fixup protocol smtp 25 breaks a number of various features with regards to ESMTP. Essentially the required commands are not forwarded to the server, commands such as X-LINK2STATE, Auth, Auth login, KILL, and WIZ are all discarded.

It should be noted that when fixup smtp is enabled, the *ONLY* valid commands are --

HELO, MAIL, RCPT, DATA, RSET, NOOP, and QUIT, and even at that case, some clients/servers are still broken.

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