I'm having this same issue now.
This doesn't happen to my other databases on another server.
Basically, I have a startup trigger that sends out mail, and I'm finding on database on a particular (new) server, UTL_SMTP is getting this error.
This is an SMTP error, that Oracle is reporting back to you. Your mail server is complaining because you did not create the email in the proper format. It could not read the FROM line in you email. You may be missing a carriage return, or the FROM address is ill-formed.