[Dovecot] Modifying the underlying maildir externally (webmail, replication)

[Tony Rutherford]

Timo Sirainen wrote:
> On 20.1.2010, at 22.21, Attila Nagy wrote:
>
>   
>> After running through http://wiki.dovecot.org/IndexFiles I'm not sure how well would Dovecot work with other programs modifying the maildirs (adding, deleting, moving messages, folders etc).
>> The "Main index" section says "The index file is synchronized against mailbox only if the syncing information changes.", where syncing information consists or cur and new directories' timestamps.
>> Does that mean I am safe there?
>>     
>
> Yes. The worst that can happen is that Dovecot doesn't see external changes for 2 seconds. And that's only if your filesystem doesn't support sub-second timestamps.
>
>   
>> Are the above right, and can Dovecot use its indexes and caches safely with others using the same maildirs?
>>     
>
> Yes. I've only recently added maildir_very_dirty_syncs=yes that improves performance but makes it work less safely when other programs modify the maildir.
>
> Although there is kind of a potential problem if other programs modify the maildir without locking. http://wiki.dovecot.org/MailboxFormat/Maildir#Locking but that isn't unique to Dovecot. That would cause problems with all programs accessing maildir. Dovecot just logs an error about it, instead of silently giving broken information to IMAP clients.
>   
We have the exact same configuration, and we had similar concerns.  I'm 
happy to say that we (so far) have been pleasantly surprised by how well 
Dovecot handles this situation and keeps its index files in synch while 
other 3rd parties (web, etc.) are changing the Maildirs.  It seems very 
reliable, and we haven't seen any problems.

Tony