message-syntax-checks

message-syntax-checks is a variable defined in `message.el'.
Its value is

((sender . disabled))

Documentation:
*Controls what syntax checks should not be performed on outgoing posts.
To disable checking of long signatures, for instance, add
`(signature . disabled)' to this list.

Don't touch this variable unless you really know what you're doing.

Checks include `approved', `bogus-recipient', `continuation-headers',
`control-chars', `empty', `existing-newsgroups', `from', `illegible-text',
`invisible-text', `long-header-lines', `long-lines', `message-id',
`multiple-headers', `new-text', `newsgroups', `quoting-style',
`repeated-newsgroups', `reply-to', `sender', `sendsys', `shoot',
`shorten-followup-to', `signature', `size', `subject', `subject-cmsg'
and `valid-newsgroups'.

You can customize this variable.