Teams and maillists

After resolving a confusing support ticket we have identified that some University members were adding maillists to Teams: please do not ever try to add a maillist email address to a Team. It won’t do what you want and it has adverse effects.

Why? In part it’s because the Maillist service (Sympa) and Nexus365 are entirely separate. There is no integration at all – they’re run as separate services and they’re managed by different staff within IT Services. We believe that what is happening is someone assumes that adding a maillist’s address to a Team would be a quick and simple way to populate it.

It isn’t, and it doesn’t.

Here’s why:
  1. Maillist/Sympa is an external organisation, as far as Nexus365 is concerned. Any maillist address you add is treated like any other external user account with a non-nexus address. Teams (and other Nexus365 services) do not see a maillist’s address as a bulk list of users. It has no way to expand the list and see its membership. Instead, Nexus365 would assume that you are adding ONE user. It is entirely unaware that the email address you’re adding has any connection with a bulk senders list.
  2. Anyone in the maillist can receive the welcome email from Teams which invites them to join the Team, whether or not they’re part of the University.

This is where the problem begins, particularly if – as has happened in a few of the examples we’ve looked into – that user attempts to specify their own Oxford address as the recipient address for this external account. This is not something we can limit without hindering external collaboration in Teams works for the whole University.

When you add a maillist to a Team, what you’ve actually done is generate a code for that user to join your team, but which has now been emailed to the maillist’s entire membership. So under these circumstances anyone can use that code and take up that presence in your team rather than the genuine Nexus365 account. This causes a conflict which we have to unpick (by deleting the errant account entry).

The maillist account only becomes seriously problematic in a Team IF someone receives the invite, AND goes through the process to validate and join that account in teams. A Team Owner can remove the errant entry (which will show as an external user) from your Team themselves, without IT Services’ intervention. We only need to be involved if a maillist member has responded to the welcome message. 
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N.B. To prevent this specific issue recurring the Nexus Team are now pre-emptively blocking the addition of the University’s maillist domain names from being added to a Team’s membership.
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If you want to bulk add users to a team, consider using the methods detailed in the Power Automate (Flow) User Group Thread. Microsoft is working on a method of using .CSV imports for Teams and group memberships but there has been no news yet on a date for release. In the meantime the PowerAutomate “join to group” or “Join to team” methods are the only ones available.
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