M S C the help file in
FEATURE: Scramble the Message-ID When Sending
Normally the Message-ID header that Alpine generates when sending a
message contains the name of the computer from which the message is
being sent. Some believe that this hostname could be used by spammers
or could be used by others for nefarious purposes. If this feature is
set, that name will be transformed with a simple Rot13 transformation.
The result will still have the correct syntax for a Message-ID but the
part of the MessageID that is often a domain name will not be an
actual domain name because the letters will be scrambled.
It is possible (but unlikely?) that some spam detection software will
use that as a reason to reject the mail as spam. It has also been
reported that some spam detection software uses the fact that there
are no dots after the "@" as a reason to reject messages. If your
PC-Alpine Message-ID is using a name without a dot that is because
that is what Windows thinks is your "Full computer name". The method
used to set this varies from one type of Windows to another but check
under Settings -> Control Panel
-> System and look for Network Identification or Computer Name or something similar. How to set it is beyond the scope of Alpine.
which seems to both scramble the
message-id field and, apparently, obviates the need for a
sender field (at least from
alpine). In this way, the
sender field is side-stepped.