dovecot - Aug 2012 - Size of Mailbox affecting the sending of mail?

Hi,

I didn't know where to post this one so I'll start off with you guys and
then try Postfix if I'm barking up the wrong tree!

Having set up my mail server (Dovecot/Postfix), users are experiencing 
long delays (a couple of minutes) when sending mail from mail client 
such as Thunderbird - this increases with attachments. Having had a 
brief discussion with someone, they mentioned that the reason that this 
may be to do with the size of the mailbox. I couldn't see the rationale 
behind this unless Dovecot is syncing the mailbox after every sent mail 
(due to possibly saving the sent item?) The mail is being delivered 
successfully but the amount of time it is taking to complete the action 
is far too long!

Sorry this is a bit vague but any advice on trying to diagnose the 
problem would be appreciated.

Thanks in advance!

Tim

Am 24.08.2012 12:53, schrieb Tim Smith:
> Hi,
> 
> I didn't know where to post this one so I'll start off with you
guys and
> then try Postfix if I'm barking up the wrong tree!
> 
> Having set up my mail server (Dovecot/Postfix), users are experiencing
> long delays (a couple of minutes) when sending mail from mail client
> such as Thunderbird - this increases with attachments. Having had a
> brief discussion with someone, they mentioned that the reason that this
> may be to do with the size of the mailbox. I couldn't see the rationale
> behind this unless Dovecot is syncing the mailbox after every sent mail
> (due to possibly saving the sent item?) The mail is being delivered
> successfully but the amount of time it is taking to complete the action
> is far too long!
> 
> Sorry this is a bit vague but any advice on trying to diagnose the
> problem would be appreciated.
> 
> Thanks in advance!
> 
> Tim
sending mail ist usual smtp ( postfix ), not dovecot
if no firewalls/proxies , slow lines , dns problems are involved, there
may exist some policy or milter service which slows down smtp out from
i.e tb, ask same question with logs and config in the postfix mail list
size of mailbox should be not involved in this
-- 
Best Regards
MfG Robert Schetterer

Am 24.08.2012 13:35, schrieb Jahnke-Zumbusch, Dirk:
> Hi all,
> 
>>>> Having set up my mail server (Dovecot/Postfix), users are
experiencing
>>>> long delays (a couple of minutes) when sending mail from mail
client
>>>> such as Thunderbird - this increases with attachments. Having
had a
> 
> While in the first place sending e-mail has to do with SMTP and not IMAP,
> most mail client programs are configured to save a copy of an e-mail using
> FCC (file carbon copy) by putting this copy via IMAP into some
"Sent"
> folder. And here you are: this may explain the long delays, esp. if on
> some asymmetric connection like DSL with low upstream bandwith.
> 
> Just my 2c
> 
> Cheers and have a nice weekend
> 
> 
> --
> Dirk Jahnke-Zumbusch              Deutsches Elektronen-Synchrotron DESY
> 
very true, but tb should show the copy action, unless its not configured
not to do so

-- 
Best Regards
MfG Robert Schetterer

On 8/24/2012 5:53 AM, Tim Smith wrote:

Hay Tim,
> Having set up my mail server (Dovecot/Postfix), users are experiencing
> long delays (a couple of minutes) when sending mail from mail client
> such as Thunderbird - this increases with attachments. Having had a
> brief discussion with someone, they mentioned that the reason that this
> may be to do with the size of the mailbox. I couldn't see the rationale
> behind this unless Dovecot is syncing the mailbox after every sent mail
> (due to possibly saving the sent item?) The mail is being delivered
> successfully but the amount of time it is taking to complete the action
> is far too long!
You probably have multiple factors involved in this mail sending delay
issue.

One may be that you're not bypassing your Postfix restrictions on your
submission service.  To fix this, disable your restrictions in the
master.cf service definition of your submission service.  For example:

587      inet  n       -       n       -       -       smtpd
        -o smtpd_enforce_tls=yes
	-o smtpd_sasl_auth_enable=yes
        -o content_filter        -o smtpd_client_restrictions        -o
smtpd_helo_restrictions        -o smtpd_sender_restrictions        -o
smtpd_recipient_restrictions=permit_mynetworks,\
	   permit_sasl_authenticated,reject
        -o receive_override_options=no_unknown_recipient_checks,\
	   no_address_mappings,no_header_body_checks

This should squash any/all delays in Postfix submission.

Another is the fact you're storing the users' Sent folders on the IMAP
server.  Typically there's nothing wrong with this.  I do this and I see
zero delay in Tbird.  If a good portion of the delay you're seeing is
Tbird copying messages to the Sent folder then I'd say you may have a
duplex mismatch or some other network layer issue.

What is the network topology between these client MUAs and the server?
Full duplex fast ethernet?  GbE?  Or is the server at a remote location,
say a colo/VPS server, and your clients are submitting over a shared
ADSL/cable circuit to the server?  If this is the case you'll always
have substantial delays as the real outbound transmission rate of the
best ADSL/cable circuits is only 500-1000 Kbps.  Sending an attachment
over such a pipe is always going to be slow, doubly so if you're copying
to an IMAP Sent folder over the same connection, plus sharing it for web
browsing, etc, amongst many users.

If this is a SOHO environment with shared ADSL/cable the server needs to
be on site, with clients connected via ethernet.  This will allow
instantaneous submission and Sent copying, while pushing the delay to
the Postfix outbound queue, where it's invisible to your users.

-- 
Stan

On 24.8.2012, at 13.53, Tim Smith wrote:
> Having set up my mail server (Dovecot/Postfix), users are experiencing long
delays (a couple of minutes) when sending mail from mail client such as
Thunderbird - this increases with attachments. Having had a brief discussion
with someone, they mentioned that the reason that this may be to do with the
size of the mailbox. I couldn't see the rationale behind this unless Dovecot
is syncing the mailbox after every sent mail (due to possibly saving the sent
item?) The mail is being delivered successfully but the amount of time it is
taking to complete the action is far too long!
Other than the bandwidth others already mentioned, the only reason it could be
Dovecot's fault is exactly the size of the Sent mailbox. How large is that
and what mailbox format are you using?