Email to local user aliases on the host server is failing

[ghost]

I am struggling to get email from the local system into mailcow. I have followed the local MTA docs but it is still failing, the logs (extract below) report the mailname being the same as the mailcow hostname. This used to be true but I recently updated the MAILCOW_HOSTNAME to fix this.

This only happens when I am sending to an alias (/etc/aliases (root,postmaster,logcheck))
When I send direct to a normal email address it works fine.

Apr 11 08:02:08 mail01 postfix/smtp[12965]: warning: host ex1.example.com[198.51.100.1]:25 greeted me with my own hostname mail01.mydomain.com
Apr 11 08:02:08 mail01 postfix/smtp[12965]: warning: host ex1.example.com[198.51.100.1]:25 replied to HELO/EHLO with my own hostname mail01.mydomain.com
Apr 11 08:02:08 mail01 postfix/smtp[12965]: 12C6517A66D: to=<logcheck@ex1.example.com>, relay=ex1.example.com[198.51.100.1]:25, delay=0.03, delays=0.01/0.01/0.01/0, dsn=5.4.6, status=bounced (mail for ex1.example.com loops back to myself)

Has anyone else got this working?
Perhaps something is missing from my set up?

[stale]

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[lazyfrosch]

Basically ensure the host is a different hostname and doesn't retrieve mail for the name of the mailcow system.

myhostname = notmailcow.mydomain.com
myorigin = notmailcow.mydomain.com
mydestination = $myhostname, localhost.lazyfrosch.de, localhost
relayhost = 172.22.1.1

My host is a Debian stretch with Postfix.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.