Running through the RFC5322 lint header checking site (referenced earlier)....
This is the result of the emails sent from the forum
UNKNOWN: unknown header 'Delivered-To' at line 3
ERROR: Missing mandatory item 'from' in header 'Received' at lines 4-5
UNKNOWN: unknown header 'X-Spam-Checker-Version' at line 6
UNKNOWN: unknown header 'X-Spam-Level' at line 7
UNKNOWN: unknown header 'X-Spam-Status' at lines 8-9
WARNING: nested comments unwise in header 'Received' at lines 10-15
UNKNOWN: unknown header 'X-Mailer' at line 20
WARNING: duplicate header 'From' at line 21
WARNING: use SMTP MAIL FROM/return-path instead of non-standard errors-to in
header 'Errors-To' at line 22
UNKNOWN: unknown header 'X-Mailer' at line 23
WARNING: duplicate header 'Reply-To' at line 28
OK: found part text/plain line 31
WARNING: Content-Transfer-Encoding mislabelled as 8-bit when 7-bit suffices,
line 33
And when pasting in an email I have sent (to a gmail) address using my thunderbird desktop client, using the same smtp server:
UNKNOWN: unknown header 'Delivered-To' at line 3
ERROR: Missing mandatory item 'from' in header 'Received' at lines 4-5
UNKNOWN: unknown header 'X-Spam-Checker-Version' at line 6
UNKNOWN: unknown header 'X-Spam-Level' at line 7
UNKNOWN: unknown header 'X-Spam-Status' at lines 8-9
WARNING: nested comments unwise in header 'Received' at lines 10-15
WARNING: line too long in header 'User-Agent:' at line 19
UNKNOWN: unknown header 'User-Agent' at line 19
UNKNOWN: unknown header 'X-Forwarded-Message-Id' at line 25
OK: found default part text/plain line 27
So looking at that, it seems from the 'duplicate header' line onwards is where the forums headers diverge.
UNKNOWN: unknown header 'X-Mailer' at line 20
WARNING: duplicate header 'From' at line 21
WARNING: use SMTP MAIL FROM/return-path instead of non-standard errors-to in
header 'Errors-To' at line 22
UNKNOWN: unknown header 'X-Mailer' at line 23
WARNING: duplicate header 'Reply-To' at line 28
OK: found part text/plain line 31
WARNING: Content-Transfer-Encoding mislabelled as 8-bit when 7-bit suffices,
line 33
So there's a few things there. Are we duplicating the "Reply-To" header in FUDforum?