Dear Lars-Johan Liman,
Thank you very much for your kind and exhaustive reply. I read in the
Gnus manual:
If you have no idea what to insert for "yourmachine.yourdomain.tld",
you’ve got several choices. You can either ask your provider if he
allows you to use something like yourUserName.userfqdn.provider.net, or
you can use somethingUnique.yourdomain.tld if you own the domain
yourdomain.tld, or you can register at a service which gives private
users a FQDN for free.
None of these apply to me. Then I read just below:
Finally you can tell Gnus not to generate a Message-ID for News at all
(and letting the server do the job) [...] you can also tell Gnus not to
generate Message-IDs for mail by saying:
//there's some code here//
, however some mail servers don’t generate proper Message-IDs, too, so
test if your Mail Server behaves correctly by sending yourself a Mail
and looking at the Message-ID.
This is perfect! So I customized message-required-mail-headers. Now your
explanation shows why I should not remove the mail headers, but still I
wonder about the meaning of the lines cited above from the Gnus manual.
And I also wonder what is the meaning of the variable
message-required-mail-headers if it's essentially ignored by Message
when I remove the Message-ID header from the list.
Anyway now I'm back to the original problem where I don't know what to
insert for Message-ID because the recommendations from the Gnus manual
above don't apply, and also I can't understand how Message generates the
portion which comes before the at-sign...
And by the way, the standard for me would be
fedora.mail-host-address-is-not-set . Is this even a fully qualified
domain name, without extension? And how would I set mail host address?
Because I can only find the variable mail-host-address which is set to
system-name, which is fedora. Therefore I would expect the Message-ID to
be fsfxxxxxxx@fedora
(which by the way I think would miss the extension). If I set
mail-host-address manually to fedora.ext, would Message-ID then be
fsfxxxx...@fedora.ext? Then why don't they say
mail-host-extension-is-not-set rather than mail-host-address-is-not-set
in the default Message-ID when the mail-host-address *is* set but has no
extension? So much confusion.
On 09.12.2023 08:03, Lars-Johan Liman wrote:
Hi!
Message-ID is one of the very few _mandatory_ header lines, so a
message
without one is not a valid RFC 5322 (the sucessor of RFC 822) message.
Therefore the message "must not/cannot" leave your computer without
one.
It has to be set on the computer if it's being shipped by a
mail-related
protocol ((E)SMTP/LMTP/IMAP/POP[23]/...).
What you _can_ do (if I remember my sendmail.cf right, it's been a few
years since I taught that course ... ;-) ) is to _modify_ the
Message-ID
header in your mail server. "If it looks like it's coming from the
computer, then modify Message-ID to look like ... (bla)". But I
wouldn't
recommend it. Message-ID is supposed to be set by the sending software
(the Mail User Agent (MUA)) and it's supposed to uniquely identify the
message across all messages in the world ... ever. Modifying it would
make it very difficult to trace and debug how the message traverses the
Internet (which includes your computer). You can probably also
influence
exactly how Emacs generates the Message-ID, but again, it's probably
not
a good idea to mess with that.
Can I ask what problem you see with having your Emacs generate the
Message-ID?
Best regards,
/Lars-Johan Liman