Error: o_stream_send_istream and Disconnected in APPEND

Alessio Cecchi alessio at
Mon Jul 15 17:03:58 EEST 2019

Il 11/07/19 23:31, Timo Sirainen ha scritto:
> On 11 Jul 2019, at 10.13, Alessio Cecchi via dovecot 
> <dovecot at <mailto:dovecot at>> wrote:
>> Hi,
>> I'm running some Dovecot servers configured with LVS + Director + 
>> Backend + NFS and version (a7d78f5a2).
>> In the last days I see an increased number of these error:
>> Error: 
>> o_stream_send_istream(/nfs/mail/ 
>> <>) 
>> failed: Broken pipe
>> always with action "Disconnected in APPEND", when users try to upload 
>> a message in Sent or Drafts.
> I think it simply means that Dovecot sees that the client disconnected 
> while it was APPENDing the mail. Although I don't know why they would 
> suddenly start now. And I especially don't understand why the error is 
> "Broken pipe". Dovecot uses it internally when it closes input 
> streams, so it's possibly that, but why would isn't that happening 
> elsewhere then.. Did you upgrade your kernel recently? I guess it's 
> also possible that there is some bug in Dovecot, but I don't remember 
> any changes related to this for a long time.
> I guess it could actually be writing as well, because "Broken pipe" is 
> set also for closed output streams, so maybe some failed NFS write 
> could cause it (although it really should have logged a different 
> error in that case, so if that was the reason this is a bug).
> Dovecot v2.3.x would log a different error depending on if the problem 
> was reading or writing, which would make this clearer.

Thanks Timo,

the operating system is CentOS 6 from years, and we doing regular update 
every time available. And also the NFS storage is the same from years.

The error is not starting to show now, I see it occasionally since 2017 
but after the last network upgrade (Firewall and Switch) are coming more 
frequently. And only for Thunderbird and sometimes Apple iOS Mail.

The error never occurred on old servers when we didn't have a physical 
firewall, but we used iptables on individual servers, and MTU on network 
interfaces ha MTU 9000, but many others components was updated in the 

We will upgrade to Dovecot 2.3 in the next months.

Alessio Cecchi
Postmaster @

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