Description:
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My php script walks a collection mailboxes to perform an imap_search. When I open each mailbox using imap_open the results are always correct. imap_open however is very slow so I started to use imap_reopen. 

Unfortunately imap_search now often does not find anything anymore. Sometimes it finds them all, sometimes only in some of the mailboxes but most of the time it finds nothing.

Restarting apache or dovecot (imap server) does not make any difference.

Doing an imap_open after 5 times imap_reopen make the script show more results but still not all of them.

Test script:
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$reopened = imap_reopen($stream, $current_mailbox['mailserver'].$val['name'], OP_READONLY);
if($reopened) {
  $emails = imap_search($stream, $imap_pattern, SE_UID);
  ...
}

Expected result:
----------------
bot after imap_open as well as after imap_reopen the imap_search function should be able to find the mails.