IT Services

Nexus forwarding, split routing and mailloops


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 IT Services 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 and 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 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

2. Routing changes

What happens when Fluffy asks for to route to and not to Nexus at all?

HelpCentre/ITSS change the routing for the OxMails goes to 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.

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

When the address on a Nexus account is for an Oxford domain that IT Services do not manage (eg ie they wont be in the Mailer tables but

If ITSS or HelpCentre staff...

  • record the address in the IT Services database via WebReg or ITSS info
  • AND give the Nexus account math1234 the sending address of eg

Nexus processes will.....

  • Add the forwarding to math1234 which looks like Forwarding to :
  • Mail sent from other Nexus accounts to will go to math1234@nexus which will then forward it to the real
  • math1234@nexus cannot have a forward of just 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 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 domain to be able to set on the account. 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.