Placed a real animated gif in the directory, and there is no output in the error_log when trying to send a personal msg. Still the error msg is at the top of the screen.
access_log is "POST /?qa=message/user_name HTTP/1.1" 200
No emails about the msg.
The user's email account is valid.
The admin is receiving emails about new questions, so I guess the mail is functioning properly.
What can I do now?