Moving an existing Mail Relay from one VM to another.

Mark Sapiro mark at
Wed Mar 17 17:51:26 UTC 2021

On 3/17/21 1:48 AM, Andrews, Vincent wrote:
> We moved the IP Address from the existing VM to the new and changed
> /etc/hostname and rebooted.
> We then noticed that mail was being delayed by two key 365 domains. We
> left it like that for about 40 minutes and then reverted to the existing
> server. After which mail was processed correctly. The messages in
> /var/spool/mqueue were moved to the existing system and within 10
> minutes everything was cleared.
> Has anyone had a similar experience?

There are always issues with new mail servers whose IP address has not
yet developed a reputation, but IIUC, from the remote's point of view,
the IP hasn't changed.

> Could it be that the new VM – having a different MAC address – was being
> flagged as an illegal mail relay?

And how would the remote SMTPD server determine the MAC of the sending
server? I don't think that's possible. I don't know why there would be
an issue if the IP didn't change. What is the content of the 4xx
responses from the remote?

Mark Sapiro <mark at>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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