[fetchmail-devel] [PATCH] handle imap EXPUNGE better

[Sunil S. <sh...@bo...>]

A good imap server can handle two email clients accessing the same
mailbox and reports the mails deleted by one email client correctly to
the other email client.

However, fetchmail cannot handle this unexpected deletion of mails.
This is because fetchmail caches which mails are new and the size of
those new mails. This caching is required to give a better
performance, but leads to unexpected results when another email client
is writing to the same mailbox:

- An old mail could be delivered instead of a recent mail.

- fetchmail passes the wrong size to the SMTP server in the MAIL FROM:
  command. If the SMTP server has size restrictions, a wrong mail will
  get rejected!

- "fetchmail -vv" reports that there is a mismatch in the expected and
  received message sizes.

This patch causes fetchmail to quit the poll if there is a mismatch in
the count of mails being deleted.

This patch also handles servers which do not report RECENT on EXPUNGE
in a better way. Now, recentcount is counted down on EXPUNGE of each
mail along with count. This way, recentcount need not be reset to zero
if the server does not give a new report of RECENT mails.

This patch has been tested by running two fetchmails on the same
mailbox!

-- 
Sunil Shetye.