Sender address rejected: Common domain forgery

[postcd]

Hello,

when i send mail from gmail on behalf of my external mailbox (and its SMTP), mail goes to a remote server (cpanel exim dovecot?) of the recipient, but this server forwards it to someone elses gmail (because cpanel user probably set forwarding of the mail) , but gmail seems to deny the delivery with mentioned error 550.

this is what cpanel mail server (of the recipient) says:

** [email protected] ([email protected]) <[email protected]> R=dkim_lookuphost T=dkim_remote_smtp H=gmail-smtp-in.l.google.com [172.217.197.26]: SMTP error from remote mail server after RCPT TO:<[email protected]>: 550 5.7.1 <[email protected]>: Sender address rejected: Common domain forgery

I do not know how to solve this in cpanel (my smtp server and recipient mail server both are using cpanel) so Gmail accept the mail and do not detect forgery which seems like a false positive, isn't it?

 

[cPanelLauren]

Hello @postcd


This sounds like an issue that would be best addressed by google You can reach their postmaster section here: Postmaster Tools – Google

 

[postcd]

Someone tried to send e-mail from gmail to my cpanel mailbox and he seen same error as above:
Can this be caused by cloudflare, missing SPF record in cPanel? I bet SPF is not used when e-mail is not send out of cpanel, only received and then downloaded by POP3 to my protonmail mailbox.

From exim log:

SMTP error from remote mail server after RCPT TO:<[email protected]>: 550 5.7.1 <[email protected]>: Sender address rejected: Common domain forgery

it seems that destination google mailbox thinks that the sender attempt to pretend to be [email protected], so u think it have to be some misconfiguration on the cpanel server whcich gives destination google server reason to think so?

I think the problem may be cPanel "Email Filters" feature (mail/filters/userfilters.html) where i had set a rule which redirect all e-mail to my gmail mailbox. After disabling it, text mail went thru without triggering Gmail antispam. If cPanel want, check this to see if it can be prevented or if that is the issue.

UPDATE: when i removed the cPanel / "Email filter" which forwards all mail to my gmail mailbox, then google no longer block the mail - it is strange, is there anything for cPanel to fix?