iPhone/iPad IMAP connection bursts causes user+IP exceeded

[Robert Giles]

Apologies for bumping Joseph Tam's rather old thread, but I'm wondering 
if anyone has come up with a workaround/fix for this problem that iOS 
Mail.app clients (10.3.3, 11.0.3, 11.1?) continue to exhibit?

Robert



On 10/28/2016 at 03:49 PM, Joseph Tam wrote:
> I frequently see this from my iPhone/iPad IMAP users:
> 
>      Oct 24 21:30:55 server dovecot: imap-login: Login: user=<user>, ...
>      [... repeated 10 times ...]
>      Oct 24 21:32:54 server dovecot: imap-login: Maximum number of 
> connections from user+IP exceeded (mail_max_userip_connections=12): 
> user=<user>
>      Oct 24 21:32:54 server dovecot: imap(user): Logged out ...
>      [... repeated 11 times ...]
> 
> These bursts of logins/max/logouts would cycling on for a few minutes.
> Googling this problem seems to turn up lots of similar complaints about
> iOS mail mail clients. e.g.
> 
>      https://discussions.apple.com/thread/2547839?tstart=0
> 
> iOS mail readers do not limit connections limit as other mailreaders
> can.  I could increase mail_max_userip_connections, but that just moves
> the goal posts.
> 
> Using the new rawlog feature in 2.2.26 (thanks Dovecot team!), I was able
> to see that these connection bursts are caused by clients doing global
> searches.  The rawlogs show each mailbox being SELECT'd and searched
> (e.g. From header string):
> 
>      1477369968.730450 2 ID ("name" "iPad Mail" "version" "13G36" "os" 
> "iOS" "os-version" "9.3.5 (13G36)")
>      1477369968.781932 3 SELECT {mailbox}
>      1477369968.961636 4 UID SEARCH RETURN (COUNT) 1:* NOT DELETED
>      1477369969.006087 5 UID SEARCH RETURN (ALL) 1:* NOT DELETED
>      1477369969.052701 6 UID SEARCH RETURN (ALL) {search-term} NOT DELETED
>      1477369974.624153 7 LOGOUT
> 
> Questions:
> 
>      1) How does this affect the user?  I heard from one user that it
>      makes global searches unusable because his reader just spins its
>      wheel.  I'm not sure whether this is impatience or this results
>      in failed searches.
> 
>      2) Is there a client-side fix (e.g. connection limiting)?
>      Apple appears to be intransigent on addressing this.
> 
>      3) Will maintaining search indices (e.g. solr) help with this?
>      Maybe the searches are taking too long and the connections pile
>      up waiting for previous searches to finish.
> 
> Thanks,
> Joseph Tam <jtam.home at gmail.com>

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