4.2.5 Reply Codes After DATA and the Subsequent <CRLF>.<CRLF>
When an SMTP server returns a positive completion status (2yz code)
after the DATA command is completed with <CRLF>.<CRLF>, it accepts
- delivering the message (if the recipient mailbox exists), or
- if attempts to deliver the message fail due to transient
conditions, retrying delivery some reasonable number of times at
intervals as specified in section 4.5.4.
- if attempts to deliver the message fail due to permanent
conditions, or if repeated attempts to deliver the message fail
due to transient conditions, returning appropriate notification to
the sender of the original message (using the address in the SMTP
If it's spam, the email should be rejected while the SMTP connection is still established with an error code (4XX or 5XX). If the email was accepted for delivery, there are really only two options: deliver the email or bounce it back to the sender.