Steffen,

I apologize for missing your helpful message - I wasn't intentionally ignoring 
it. One of the artifacts of my mail issues is that mail disappears, this 
included.  

-------- Original Message --------
Subject: Re: Dovecot 2.2.16: disappearing messages, mismatched summaries, 
duplicated messages, excessive full re-downloads
From: Steffen Kaiser <[email protected]>
To: David Gessel <[email protected]>
Date: Fri Apr 24 2015 10:29:46 GMT+0300 (Arabic Standard Time)

> On Thu, 23 Apr 2015, David Gessel wrote:
> 
>> I'm inclined to believe, as trivial as it may be to enumerate, that:
> 
>> Something is triggering dovecot to believe the indexes need to be rebuilt.
>> When checking mail during the rebuild, clients get confused by UIDs in 
>> transition.
> 
>> I would think that sdbox would alleviate these issues, no?
> 
> The real problem is that you do not know _why_ "Something is triggering 
> dovecot to believe the indexes need to be rebuilt".

I'm not 100% sure that's what is happening.

> 
> This is the same for sdbox and mdbox, IMHO.

that would be sad - but I haven't tried that yet.

> 
> That's why I asked about if some external process is trying to change the 
> mail storage. Is there something except Dovecot that changes the mtime of the 
> directories "new", "cur" or Maildir base?

Not that I am aware of.  this is a jail only running mail.

> Do you deliver messages without Dovecot LDA/LMTP? 

Dovecot LDA only.

>Do you store different information in the Maildir? 

nothing not part of Dovecot's processes - but the full text index files are 
also stored there.

> Do you (not) have separate mail storage and user home directories? 

Virtual mail configuration - home directories are completely isolated.  Nothing 
happens in /mail that isn't mail related.

> Do you run a virus checker on file system level?

no, but amavisd calls clamAV on inbound messages.

> 
> Do you run two Dovecot instances on the same server, maybe as left over from 
> some testing or crash?

certainly not intentionally and I'm pretty confident not actually; these issues 
survive many reboots without much variation, so not from testing.

> 
> -- Steffen Kaiser


Some updates to the process:

I experimented with all variations of Mail processes values with no real 
improvement - some perhaps but likely as not just observational variations 
rather than meaningful data.  Specifically in 10-mail.conf:
 mmap_disable = yes
 mail_fsync = always
 lock_method = flock  

I'm probably suffering from confirmation bias, but I think things got a little 
bit better.

However, I still got double messages in TB and K9 on some checks.  Then I 
looked at the IMAP capability string returned from telnet localhost 993.  It 
didn't include NAMESPACE.  The post-login enumeration did, but not the 
pre-login.  

adding
imap_capability = +NAMESPACE
to 20-imap.conf
seems to have cleared up the appearance of double entries in clients.  I had 
one message's header/display get confused (another symptom of the issues) but 
given the problems my local client database is pretty scrambled.  when I have a 
decent network connection for a few days, I'll try recreating my client 
database and see if that helps.

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