I need to write php code to identify common e-mail errors, like "inbox full" or specially "invalid email name" from email messages, because we need to clear our databases from nonexistent emails.
I'm looking the MIME and IMF formats but I didn't find any kind of standard error code, does it exist?
This may help:
http://www.unixhub.com/docs/email/SMTPcodes.html
There are a lot of RFCs for email, and error codes.
The one you specified may be (550)