dovecot - Jun 2020 - How to use dovecot only as POP3 server / prevent it from creating .imap directories?

Dear all,

on our mail server, I let sendmail deliver incoming messages to a file in mbox
format called "inbox" in each user's home directory.  Now I would
like to use dovecot as POP3 server so that users can let their MUA download
their messages via POP3. I do not want to use any IMAP functionality.

The POP3 part works with the configuration shown below, but nevertheless there
is a problem which is a show stopper:

Although I think I have turned off IMAP (e.g. no IMAP listener), dovecot still
creates .imap directories and does so in a very weird way. It creates one .imap
subdirectory in every subdirectory of each user's home directory, and for
every file in each user's home directory creates an additional subdirectory
with the same name in its .imap directories. It does this recursively, and 1000
files in a user's home directory would mean 1000 additional subdirectories.

Of course, I can't live with that. I know that the dovecot documentation
discourages using the home directory as mail location, but in my case this
should not be a problem at all if IMAP is not used. I have played around with
dovecot for several days, but could not solve that problem.

So how can I turn off IMAP completely and prevent dovecot from creating any
.imap directories or IMAP related files?

This happens with dovecot 2.3.4.1 (f79e8e7e4) on Debian buster (with all updates
applied).

My configuration (doveconf -n) is (the configuration is complete - I don't
use SQL or LDAP):

# 2.3.4.1 (f79e8e7e4): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.4 ()
# OS: Linux 4.19.0-9-amd64 x86_64 Debian 10.4
# Hostname: host.example.com
listen = aaa.bbb.ccc.ddd
mail_location = mbox:~:INBOX=~/inbox
mail_privileged_group = mail
namespace inbox {
  inbox = yes
  location   mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Junk {
    special_use = \Junk
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    special_use = \Sent
  }
  mailbox Trash {
    special_use = \Trash
  }
  prefix }
passdb {
  driver = pam
}
pop3_lock_session = yes
protocols = " pop3"
service imap-login {
  inet_listener imap {
    port = 0
  }
  inet_listener imaps {
    port = 0
  }
}
service pop3-login {
  inet_listener pop3 {
    port = 0
  }
  inet_listener pop3s {
    port = 995
    ssl = yes
  }
}
ssl = required
ssl_cert = </etc/dovecot/tls/xxxx.crt
ssl_cipher_list = DHE-RSA-AES256-GCM-SHA384
ssl_client_ca_dir = /etc/ssl/certs
ssl_dh = # hidden, use -P to show it
ssl_key = # hidden, use -P to show it
ssl_min_protocol = TLSv1.2
ssl_prefer_server_ciphers = yes
userdb {
  driver = passwd
}

Thank you very much in advance for any idea!

Regards,

Binarus

On Sun, Jun 07, 2020 at 08:44:51AM +0200, Binarus wrote:
> Dear all,
> 
> on our mail server, I let sendmail deliver incoming messages to a file in
mbox format called "inbox" in each user's home directory.  Now I
would like to use dovecot as POP3 server so that users can let their MUA
download their messages via POP3. I do not want to use any IMAP functionality.
> 
> The POP3 part works with the configuration shown below, but nevertheless
there is a problem which is a show stopper:
> 
> Although I think I have turned off IMAP (e.g. no IMAP listener), dovecot
still creates .imap directories and does so in a very weird way. It creates one
.imap subdirectory in every subdirectory of each user's home directory, and
for every file in each user's home directory creates an additional
subdirectory with the same name in its .imap directories. It does this
recursively, and 1000 files in a user's home directory would mean 1000
additional subdirectories.
> 
> Of course, I can't live with that. I know that the dovecot
documentation discourages using the home directory as mail location, but in my
case this should not be a problem at all if IMAP is not used. I have played
around with dovecot for several days, but could not solve that problem.
> 
> So how can I turn off IMAP completely and prevent dovecot from creating any
.imap directories or IMAP related files?
I suppose you'd be OK with having IMAP but having it look *only* at the 
designated mbox file.

That would be something I could use.

-- hendrik
> 
> This happens with dovecot 2.3.4.1 (f79e8e7e4) on Debian buster (with all
updates applied).
> 
> My configuration (doveconf -n) is (the configuration is complete - I
don't use SQL or LDAP):
> 
> # 2.3.4.1 (f79e8e7e4): /etc/dovecot/dovecot.conf
> # Pigeonhole version 0.5.4 ()
> # OS: Linux 4.19.0-9-amd64 x86_64 Debian 10.4
> # Hostname: host.example.com
> listen = aaa.bbb.ccc.ddd
> mail_location = mbox:~:INBOX=~/inbox
> mail_privileged_group = mail
> namespace inbox {
>   inbox = yes
>   location >   mailbox Drafts {
>     special_use = \Drafts
>   }
>   mailbox Junk {
>     special_use = \Junk
>   }
>   mailbox Sent {
>     special_use = \Sent
>   }
>   mailbox "Sent Messages" {
>     special_use = \Sent
>   }
>   mailbox Trash {
>     special_use = \Trash
>   }
>   prefix > }
> passdb {
>   driver = pam
> }
> pop3_lock_session = yes
> protocols = " pop3"
> service imap-login {
>   inet_listener imap {
>     port = 0
>   }
>   inet_listener imaps {
>     port = 0
>   }
> }
> service pop3-login {
>   inet_listener pop3 {
>     port = 0
>   }
>   inet_listener pop3s {
>     port = 995
>     ssl = yes
>   }
> }
> ssl = required
> ssl_cert = </etc/dovecot/tls/xxxx.crt
> ssl_cipher_list = DHE-RSA-AES256-GCM-SHA384
> ssl_client_ca_dir = /etc/ssl/certs
> ssl_dh = # hidden, use -P to show it
> ssl_key = # hidden, use -P to show it
> ssl_min_protocol = TLSv1.2
> ssl_prefer_server_ciphers = yes
> userdb {
>   driver = passwd
> }
> 
> Thank you very much in advance for any idea!
> 
> Regards,
> 
> Binarus

On 07.06.2020 17:56, Hendrik Boom wrote:
> On Sun, Jun 07, 2020 at 08:44:51AM +0200, Binarus wrote:
>> Dear all,
>>
>> on our mail server, I let sendmail deliver incoming messages to a file
in mbox format called "inbox" in each user's home directory.  Now
I would like to use dovecot as POP3 server so that users can let their MUA
download their messages via POP3. I do not want to use any IMAP functionality.
>>
>> The POP3 part works with the configuration shown below, but
nevertheless there is a problem which is a show stopper:
>>
>> Although I think I have turned off IMAP (e.g. no IMAP listener),
dovecot still creates .imap directories and does so in a very weird way. It
creates one .imap subdirectory in every subdirectory of each user's home
directory, and for every file in each user's home directory creates an
additional subdirectory with the same name in its .imap directories. It does
this recursively, and 1000 files in a user's home directory would mean 1000
additional subdirectories.
>>
>> Of course, I can't live with that. I know that the dovecot
documentation discourages using the home directory as mail location, but in my
case this should not be a problem at all if IMAP is not used. I have played
around with dovecot for several days, but could not solve that problem.
>>
>> So how can I turn off IMAP completely and prevent dovecot from creating
any .imap directories or IMAP related files?
> 
> I suppose you'd be OK with having IMAP but having it look *only* at the
> designated mbox file.
> 
> That would be something I could use.
Thank you very much for your comment. You are completely right - I could very
well live with that solution.

However, I have researched for many hours before posting here, but I could not
find out how to achieve this. As I have described in my first post, dovecot
created an .imap subdirectory in each directory which existed, and created one
subdirectory (within the .imap directory) for each file which existed, and it
did so recursively. Whatever portions in the configuration files I commented
out, and whatever service I disabled by other means (e.g. by giving Port = 0), I
could not prevent dovecot from messing up users' home directories
completely, i.e. I could not make it use only the mbox file and leave the
directories as-is otherwise (possibly adding a file or two for management and
housekeeping).

This is extremely weird and not acceptable; imagine 10,000 directories being
created for nothing solely because there are 10,000 files. Plus, it is a
behaviour which previous versions did not show (I have pulled over the
configuration from another system running Debian jessie, where the problem did
not arise). I still can't understand why it does IMAP things at all, given
that I have protocols = " pop3".

So how exactly do I have to alter the configuration to implement your
suggestion, i.e. to make dovecot look only at the mbox file and to prevent the
creation of unnecessary directories?

Thank you very much again,

Binarus