Article ID: 4116, created on Mar 24, 2008, last review on May 1, 2014

  • Applies to:
  • Sphera


How does Qpopper works in a VDS environment.

 .user.pop in /var/spool/mail, Can't receive E-mail because of quota, about Qpopper in server mode.



This issue is in the way qpopper works:

In normal (non-server) mode, Qpopper starts a session by locking the mail spool, copying all messages to a temporary file (i.e. .user.pop), zeroing the mail spool, then unlocking it.
At the end of the session all non-deleted messages (plus any new ones that arrived during the session) are copied back to the spool.

By working from a temporary copy of the mail spool, Qpopper
operates at the highest safety level, at the cost of extra I/O.

The problem is that the VDS quota is limited and if the mail spool of the user is to big, copping it would go over his quota and the file would not be copied completely.
That would cause the user not able to pop his mail.

There are two solutions:

1. The first solution is to increase VDS quota.
This is the recommended solution.

2. The second solution is to edit pop configuration file
( VDS/etc/.qpopper-option ) to enable parameter "set server-mode" to
set server-mode=true

In server mode, Qpopper starts a session by scanning the mail spool instead of copying it.
It works from the mail spool during the session. If at the end of the session all messages are deleted, or no changes have been made to the state of the spool or its messages, Qpopper avoids having to do any copying at all.

Because most POP clients download and delete all messages by default, enabling server mode can save a lot of server I/O. Even when users turn on leave mail on server in their POP client, most sessions do not result in any changes, again potentially saving a lot of I/O.


Questions and procedures about Qpopper in server mode.

1. What are the contributions and restrictions of server mode ?
Reduces the I/O usage where users download and delete all their messages
and by avoiding initial scan of pool when session starts (mail check
Also, from Sphera point of view, it is not creates temporary file.
The known restrictions or misbehaviors are
Usage of a mailbox by Qpopper simultaneously with any other
application can damage emails content.

2. Is it good practice to start qpopper at server mode by default ?
Server mode should be given for users with disk quota
or performance problems. The main problem with other applications
using the same files that can corrupt email data.

3. What can be done now and quickly ?
Possible to implement in any way (GUI or command line) server mode
and advise for customers with disk usage or response time problems
to use it.

4. How to run Qpopper in server mode? (procedures)

a. To run Qpopper for all VDSs of HostingDirector in server mode

 needs to change in hostdir.xml:

search for "<services>"

search for "<service>"

search for name="pop"

search for "<mode"
property,  param="-f /etc/.qpopper-options"

change it to
param="-S -f /etc/.qpopper-options" ( uppercase '-S' added )

b. To run Qpopper for certain VDS,

 needs to change VDS/etc/.qpopper-options, Just add new line as follows:
set server-mode=true


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