Really slow IMAP performance

[Håkon Alstadheim]

Den 24. feb. 2018 15:04, skrev Neil Jerram:
> Aki Tuomi <aki.tuomi at dovecot.fi> writes:
> 
>>> On 24 February 2018 at 15:47 Neil Jerram <neil at ossau.homelinux.net> wrote:
> 
> [...]
>>>>  Feb 24 10:24:24 arudy dovecot[1712]: imap(neil): Warning:
>>>> Transaction log file
>>>> /home/neil/dovecot-mail/.imap/INBOX/dovecot.index.log was locked
>>>> for 98 seconds (Mailbox was synchronized)
> [...]
> 
>> You are using mbox format. This is ... bit slow. =)
>>
>> When you move mails between mbox files, it has to rewrite the entire mbox file every time. You should probably start using maildir or sdbox instead.
> 
> Ah, right, thanks.
> 
> My INBOX file has 22990 messages.  Is the slowness that I am seeing
> definitely expected for an mbox of that size?  (It may also be relevant
> that the HDD it's stored on is pretty old now, and has been known to
> report SMART errors...)
> 
> If so, I'll start looking at how to migrate, given that my system is
> Postfix + Dovecot.  If you have any particular recommendations or
> migration pointers for a system like that, I'd appreciate them.
> 

I'd go with whatever tools you are familiar with. If you don't know
where to start, formail(1) can read an mbox and do whatever for each
mail contained therein. This, together with procmail, used to be the
go-to tools in the days before IMAP.

Theese days you'd probably want to involve your local delivery agent on
the output from formail. The lda would invoke sieve instead of procmail
if that is your thing.

Whatever you do, try to set up so you can do some tests before you blast
22000 mails to somewhere you do not want them :-)