To edit an existing group you also go to Settings → Options → Groups → Distribution groups I own. Select the group you want to edit, if you don’t see it immediately, just start typing its name in the search window and then click on the magnifying glass. You can press Clear to clear the results if you wish. Then select Edit, make your changes, and Save (or Cancel if you change your mind). If you want to delete a group, choose Delete and confirm.
Now that you know how to create, edit and delete distribution lists, here is a quick guide as to how to get the most out of them.
The basic limits of Office 365 distribution groups
A distribution group can have up to 100,000 members (organizations using AAD Connect can have up to 50,000). Each group can have up to 10 owners and each user/admin can create up to 300,000 distribution groups. If a group has 5,000 or more members then there is a maximum message size of 25MB.
Distribution groups in Office 365 can do a whole lot more than regular distribution lists
Regular distribution lists are just lists of people who receive emails. Distribution groups are groups that have access to shared resources, one of which is email. Depending on the set-up, other resources may include a shared calendar and shared access to apps such as SharePoint, Yammer, Team, Planner, OneNote, and PowerBI. Having said all that, email is still likely to be one of the most important functions of a distribution group, if not the most important function of a distribution group.
Distribution groups in Office 365 can do a whole lot more damage than regular distribution lists
Back in November 2016, there was a notorious incident in the UK, which capably illustrated just how much damage regular distribution lists can do. An employee in the National Health Service sent an email to everyone in the organization. That was some 1.5 million people.
That was bad enough and to make matters worse some of those people didn’t grasp the difference between Reply and Reply to all and so they also sent emails to about 1.5 million people with the result that the NHS’ servers ground to a halt. Distribution groups in Office 365 can do even more damage if things go wrong, so it makes sense to put solid policies in place to make sure that they are well managed and also to put processes in place to ensure that the policies are being followed as they should be.
The basics of effective distribution group management In Office 365
Unlike user-defined contact groups, distribution groups in Office 365 are managed centrally, but it is up to each organization to decide what this means in practice. In particular, does it mean by the IT team (if there is one) or by some kind of central admin team (if there is not) or does it mean by department heads or other managers?
Once you have determined this, you will then have to think about the criteria for creating distribution groups.
One of the biggest differences between “old-school” distribution lists and “new-school” distribution groups is that you can “nest” distribution lists but not distribution groups. In other words, you could create small distribution lists and then basically daisy-chain them together to make larger distribution lists. Sadly, this feature was not incorporated into Office 365 distribution groups, which means that whoever administers them is stuck with managing and editing long lists of contacts.
Other than that, however, the principles behind the effective governance of Office 365 distribution groups are pretty much the same as for the effective governance of traditional distribution lists. You need to determine what their purpose is to be clear about who should be on them and, by extension, who should not be on them.
You need a process for creating new distribution groups and managing existing ones.
In smaller organizations, it may be enough just for a designated individual to send an email to the IT team (or whoever else manages the distribution groups), but as SMBs grow larger, it tends to become increasingly beneficial to have a higher level of supervision, such as getting sign-off from a senior manager. Similarly, there needs to be a policy for managing existing distribution groups, including a process by which they are deleted if they become inactive.