We're having a little problem with sending out emails. We created a domain: amm-hosting.pl and added two emails: biuro and admin.
When we try to receive mail through a email client, everything goes well (using username: biuro+amm-hosting.pl).
But, when we try to send out an email, using the username: biuro+amm-hosting.pl, we get an error. When we use the cpanel username for SMTP auth, the message gets sent.
Why isn't our mail server accepting the biuro+amm-hosting.pl username for sending, but only for receiving?