Sender address is not allowed.

[ghost]

My email provider only accepts mail with with a special sender-argument. Therefore I have a /etc/postfix/sender_canonical file which maps the internal senders to the external sender value.
After installing zeyple, this does not seem to work anymore. I get error messages like this:

Feb 12 16:31:16 matrix postfix/smtp[672]: AB822100873: to=<[email protected]>, relay=mail.gmx.net[212.227.17.190]:587, delay=0.43, delays=0/0.01/0.4/0.03, dsn=5.0.0, status=bounced (host mail.gmx.net[212.227.17.190] said: 550-Requested action not taken: mailbox unavailable 550 Sender address is not allowed. (in reply to MAIL FROM command))

Any ideas how to fix this?

Thank you.