I'm having a fairly weird issue.
On my website I have a simple contact form. Name, email, subject, message.
The message should be sent to my domain name's email (google apps hosted). The 'from' is the form's email field.
However, depending what email address users have, the message isn't arriving. I've noticed that people who send with a gmail address, get a 'Undelivered Mail Returned to Sender' message, reason policy rejection 'SENDER_QUOTA_REJECTION'.
But, if the visitor fills out an hotmail address, then the email arrives as it should.
Any ideas? This really shouldn't happen.