OX EMail Push Introduction
Introduction to EMail Push in Open-Xchange
Abstract
In combination with OXtender_for_Business_Mobility (EAS) and OXtender_2_for_Microsoft_Outlook (OLOX2) a working mail push is very important. It is important to know, that this is a combined requirement to the mail server and the Open-Xchange server to make that happen.
Both of the listed OXtenders are accessing Open-Xchange via the USM interface (Universal Synchronization Module, which ist the package open-xchange-usm).
In summary:
- EAS uses an internal mail poll if no push available
- OLOX2 is depending on an external mail push trigger
Mail Push with OXtender_for_Business_Mobility
In addition to an externally triggered mail push, in internal mail poll initiated by the usm module is executed.
This is, how this polling can be influenced via /opt/open-xchange/etc/groupware/usm.properties:
- com.openexchange.usm.session.sync.email_pull_delay=50%
- com.openexchange.usm.session.sync.email_pull_min_delay=60000
These values are the default values.
1. defines, when an internal poll should be triggered while waiting for the client. This can be done as an absolute value (in milliseconds) or as a percentage value based on the waiting time as been specified by by the client per Active Sync Protocol (EAS). In the EAS protocol, the client specifies this time dynamically, usually between 30 seconds and 30 minutes. If an absolute time is specified here and the time set by the client is smaller, a mail poll is initiated at the end of the waiting time if not prevented by the setting of (2).
2. defines an additional minimum waiting time, which is enforced to be
followed, before an internal poll is executed. Is the value as
specified by the EAS client/protocol smaller than this value, no poll
will be executed. If 2. is set to a negative value, the internal mail
polling of USM will be completely disabled.
Examples
A
com.openexchange.usm.session.sync.email_pull_delay=50% com.openexchange.usm.session.sync.email_pull_min_delay=-1
Internal mail poll is disabled.
B
com.openexchange.usm.session.sync.email_pull_delay=50% com.openexchange.usm.session.sync.email_pull_min_delay=60000
| Client waiting time | Mail polling interval |
|---|---|
| 30 seconds | no polling |
| 90 seconds | poll after 60 seconds (!) |
| 180 seconds | poll after 90 seconds |
| 1800 seconds | poll after 900 seconds |
C
com.openexchange.usm.session.sync.email_pull_delay=120000 com.openexchange.usm.session.sync.email_pull_min_delay=60000
| Client waiting time | Mail polling interval |
|---|---|
| 30 seconds | no polling |
| 90 seconds | poll after 90 seconds (!) |
| 180 seconds | poll after 120 seconds |
| 1800 seconds | poll after 120 seconds |
D
com.openexchange.usm.session.sync.email_pull_delay=60000 com.openexchange.usm.session.sync.email_pull_min_delay=120000
| Client waiting time | Mail polling interval |
|---|---|
| 30 seconds | no polling |
| 90 seconds | no polling (!) |
| 180 seconds | poll after 120 seconds |
| 1800 seconds | poll after 120 seconds |
This example is not usefull, it should show, that property 2. has a
higher priority than property 1.
The default behaviour can be described like shown below:
client waiting time X (EAS Ping):
X < 60 s -> no internal mail poll
60 s <= X <= 120 s -> internal poll after 60 s
120 s < X -> internal poll after X/2 s
Mail Push with OXtender_2_for_Microsoft_Outlook
In OLOX2 USM does NO internal mail poll at all. There are no long running waiting requests (like with Ping in EAS). Instead, the client (Outlook OXtender) does http requests in short intervals asking for changes. This is the reason why USM does no internal mail poll but is depending on messages from the Open-Xchange server (using OSGi Events). The only exception is, when the client changes from one email folder to another one. This will initiate a sync.
Open-Xchange Mail Push implementations
There are currently two publicly available implementations of mail push.
The MailNotify_Bundle
This package only integrates with cyrus-imapd at the moment. We prepared a patch for dovecot2, but unfortunately the author is not willing to integrate it.
The MALPoll Bundle
The package open-xchange-push-malpoll simulates mail push in polling the imap server on a regular basis. This can only be recommended on small installations as it might stress the imap server.