Max message UID

[le-kazankin]

Hello,
As far as I understand, the uid of the message is returned from the message_idnr (bigint) column.

rfc 3501 (https://datatracker.ietf.org/doc/html/rfc3501#section-2.3.1.1) says that the UID must be 32-bit, the maximum value is 4294967295.

Is there any protection after exceeding the limit?
And is it planned to make a unique uid within one mailbox, and not the system as a whole?

[alan-hicks]

Version 4rev2 obsoletes 3501, though there is no change in the 32-bit reference in 2.3.1.1
The formal syntax (9) for uid only defines it as "Unique identifiers used instead of message sequence numbers"

What protection are you looking for? Although dbmail is licensed under GPL version 2 and there is no warranty, the dbmail server handles 64 bit numbers and I usually fix bugs.

There are no plans to make uids unique within a mailbox. It would be a significant amount of work to change dbmail.

Clients are outside the scope of dbmail but when I looked at PHP, intval() is os dependent, Python appears unaffected as integers have unlimited precision. Roundcube client has an existing mismatch between cache database (signed) integer storing up to 2147483647 and (unsigned) uid 4294967295. Squirrelmail doesn't use a database so interacts with the server and doesn't appear to be affected.

https://datatracker.ietf.org/doc/html/rfc9051#IMAP-ABNF

[le-kazankin]

Our email client was designed to work with 32 bit uid, that can be uniq within one mailbox (this behavior is found in dovecot, gmail, hotmail).

Also I am noticed that dbmail spends 2 values from the sequence to receive one message. So do I understand correctly that dbmail can store only 4611686018427387903 emails before receiving errors begin?

[alan-hicks]

That's a very large number and I'm not aware of any users anywhere close to that limit. It would be straightforward to bump that to a 128 bit integer as MySQL, PostgreSQL and Oracle support it.

I'll need to look into this as 32 bit numbers per user folder is an issue.