Unable to receive mail when forwarding is configured in webmail interface

Plesk for Linux kb: technical ABT: Group B

Applicable to:

A bounce email like the following is received on the sender mailbox:

CONFIG_TEXT: This is the mail system at host example.org.
I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
test@example.com: host example.com[203.0.113.2] said: 550 5.7.1
Command rejected (in reply to end of DATA command)
Records like the following can be found in /var/log/maillog:

CONFIG_TEXT: postfix/smtp[9220]: BF5C06167C: to=johndoe@example.com, relay=example.com[203.0.113.2]:25, delay=30, delays=0.01/0.02/30/0.2, dsn=5.7.1, status=bounced (host example.com[203.0.113.2] said: 550 5.7.1 Command rejected (in reply to end of DATA command))

Forwarding is configured in https://webmail.example.com or in the mail client.

Configure forwarding via Plesk interface.