Emails from site bouncing

[Coyote Keith]

Is there anything I can do about this? Getting lots of these bounce backs from user requested notifications on my site.

 Messages with multiple addresses in From:
    550 5.7.1 header are not accepted. l63si12806066pgd.265 - gsmtp

[Aleksi "Lex" Kilpinen]

Most likely, that is because you are using PHP mail, and it is transparently "forging" the sender address.
You may be able to set up your server to fix the headers from PHP mail (if you are using a legit sender address on the same domain) or switch to SMTP and remove the PHP mail from the equation.

[Coyote Keith]

It's a private server but I'll try smtp. Thanks