There are versions of
MS Outlook
out there which don't send messages compliant with
SMTP
(RFC 5322 - Section-3.6),
in as much as the mandatory “Date:” header is missing.
Quite naturally this makes them useless as a method for testing your SMTP mail system. See
this discussion for more information.
WORKAROUND: If you encounter this when testing SMTP delivery, compose your own test message and send that one to yourself.
Only two headers are compulsory in an SMTP e-mail: the “Date:” header & the “From:” header. Our servers refuse messages where either of these two are absent. The error message returned by our servers is, helpfully we think:
550-Mandatory header absent,
550 see: http://tools.ietf.org/html/rfc5322#section-3.6
Note: Some mailservers will return an imcomplete version of the above message — returning only part of it.
All tvScience customers using our SMTP posting accounts will have a “Date:” header added automatically should buggy software fail to add one itself.