To process bounces against a Gmail account, set your bounce settings as follows:

• Bounce Server: imap.gmail.com:993 OR pop.gmail.com:995
• Bounce Username: <your Gmail account username> (either 'user' or 'user@gmail.com' will work)
  
• Bounce Username: <your Gmail account password>
• Check "Yes, this is an IMAP account" only if you are using imap.gmail.com:993.
• Check "Yes, use extra mail settings" and "Other", then for Other put /ssl/novalidate-cert

You also will need to have activated IMAP access OR activated POP access in your Gmail account.

If this does not work and you get the error "Invalid remote specification" then your php_imap module has not been compiled with SSL support. You will need to ask your web host to recompile PHP and add the --with-imap-ssl option to the configure command.

If Gmail marks the bounces as spam, simply mark them as safe inside the Gmail Junk folder.