Nexus forwarding, split routing and mailloops

IT Services

Nexus forwarding, split routing and mailloops

Contents

1. Default setup
2. Routing changes
- 2.1. When the address on the Nexus account is not one that OUCS manages
3. If the address associated with the account changes
4. When we don't have an Oxford address

This document is an attempt to explain some of the fairly intricate processes that run on Nexus is an attempt to manage an issue called 'split routing'. Split routing is where mail sent from Nexus ends up in a different place from mail sent from outside Nexus. It is aimed at OUCS Help Centre Staff and ITSS. We don't pretend it is easy. Remember all addresses associated with a nexus account will be an Oxford controlled address.

1. Default setup

If someone is logged onto Nexus using Outlook via MAPI, or OWA and sends to fluffy.brown@spires.ox.ac.uk and fluffy.brown@spires.ox.ac.uk appears on an account on Nexus (ie the Sending address), then the message wont go out to the Oxmails but will be delivered directly to the Nexus account fluff0001. (There is no way for Exchange to work in any other way- it cant be forced to send mail to the oxmails.)

As long as in the mailer tables fluffy.brown@spires.ox.ac.uk routes to fluff0001@nexus then mail sent from outside Nexus will also end up in the fluff001@nexus and all is well. The mailer routings are visible in the Mail Routing tab in WebReg , and ITSS's https://register.it.ox.ac.uk/itss/mail_routing

2. Routing changes

What happens when Fluffy asks for fluffy.brown@spires.ox.ac.uk to route to fluffy@gmail.com and not to Nexus at all?

HelpCentre/ITSS change the routing for the OxMails fluffy.brown@spires.ox.ac.uk goes to fluffy@gmail.com. But what happens to mail sent from people on Nexus? It still goes to fluff0001@nexus and Fluffy's mail is in two places!!!

To try and stop this problem, a process runs on Nexus after every mailer table update (at approx 7.10,10.10, 13.10, 14.10, 19.10) which does the following.

if the sending address on the Nexus account is in the mailer tables, and is not routed to nexus, it will set an automatic forward on Nexus to where the Oxmails would send the mail. As it would now see that fluffy.brown@spires now routes to fluffy@gmail.com , it would automatically put a forward on fluff0001@nexus to go to fluffy@gmail and all Fluffy's mail will be in the one place ie gmail.
If there is already forward set on the nexus account, say to old hotmail address, then no additional forwarding will be set and the user will stay with split routing until it is fixed.
if the address on Nexus is from domain that OUCS manages, it will be look like Forwarding to : fluffy@gmail.com
if you manually remove the forward, it will be added back the next time the Nexus process runs so that the routing and the forwarding match.

2.1. When the address on the Nexus account is not one that OUCS manages

When the address on a Nexus account is for an Oxford domain that OUCS do not manage (eg physics.ox.ac.uk) ie they wont be in the Mailer tables but

If ITSS or HelpCentre staff...

record the address in the OUCS database via WebReg or ITSS info
AND give the Nexus account math1234 the sending address of eg hillow@maths.ox.ac.uk

Nexus processes will.....

Add the forwarding to math1234 which looks like Forwarding to : hillow@maths.forward.nexus.ox.ac.uk
Mail sent from other Nexus accounts to hillow@maths.ox.ac.uk will go to math1234@nexus which will then forward it to the real hillow@maths.ox.ac.uk.
math1234@nexus cannot have a forward of just hillow@maths.ox.ac.uk as Nexus would say ... 'yes I know that address it is on account math1234' and would try and deliver the mail to back to math1234@nexus and a mail loop would be set up.

3. If the address associated with the account changes

If the address associated with the account changes, the effect will depend on where the addresses are routed. If they are both to Nexus, the only effect will be on Calendering with ical/davmail which uses the email address rather than the username to make associations for sharing. See for example http://www.oucs.ox.ac.uk/nexus/calendar/iCal/davmail.xml where it refers to someones primary email address.

If the address on the account changes to one that is not routed to Nexus, then a forward will be automatically added. Even if you remove the forward it will be added back the next time the Nexus process runs!!

4. When we don't have an Oxford address

There are certain situations where we don't have an email address in the .ox.ac.uk domain to be able to set on the account.

from non-maintained depts where that dept does not issue an email address eg Computer Sciences don't issue addresses for new visitors
from OUP
where there is no mail routing set up for whatever reason eg retired/ nomail

The default in this case is username@nexus. This is not something we want to perpetuate and we will be looking at ways to remove these accounts by detaching mailboxes and setting the account status to 'User' rather than 'UserMailbox' or 'MailUser' , or for active users, or negotiating with the dept to get an address assigned.