Limit was 100 then 250 then 350 but now 300
Updated June 3, 2020
The Microsoft Teams service is experiencing heavy demand at present with the number of active users growing strongly. Microsoft has had to adjust some features to ensure that service levels are maintained, but they’re also using some of the saved resources to allow higher limits to some features. One such example is the increase in the participant limit for group chats, which was previously lifted earlier this month from 100 to 250. The previous 100 limit lasted a year before it was increased.
On May 27, Microsoft bumped the limit for Teams meetings (including meeting chats) to 350, but said that this was only on a temporary basis. At the time, Microsoft said that they would assess the effect of the new limit over time and decide in September if the increase should remain. One week later (June 2), Microsoft announced a reduction of the limit to 300 in an update to Office 365 notification MC214350. On the upside, the temporary nature of the increase appears to be lifted as there’s no mention about assessing the new limit in September.
According to MC214350. Microsoft has started to roll out the new limit with the goal of having it effective worldwide by the end of June. No doubt the new limit will be popular with the large enterprises who have deployed Teams, including Microsoft’s own deployment where many online meetings hit the limit and stop others being able to join.
The Downside of Large Chats
Microsoft has plenty of experience running large-scale meetings. Teams Live Events currently cater for up to 20,000 attendees (again a temporary bump from the 10,000 norm), so increasing the limit for meeting attendees to 350 shouldn’t be too much of a stretch.
Large group chats are different. Teams already limits some of the functionality available in group chats once the number of participants passes 20:
- Outlook out-of-office replies and Teams status messages are not displayed for participants.
- The indicator showing that someone is typing a message is disabled.
- Video and audio calls can’t be started in the chat (but you can schedule a Teams meeting and send everyone a link to allow them to attend).
- Sharing of documents (using OneDrive for Business) isn’t allowed.
- Read receipts for messages don’t work.
These features are restricted to reduce the strain on the service. Fetching out-of-office information for many participants requires a lot of interaction with Exchange Online mailboxes while tracking who’s read a message for the same number consumes many processing cycles.
Lots of Duplicate Compliance Records Captured
The need to capture compliance records for conversations imposes another demand. When someone posts to a group chat, the Microsoft 365 substrate captures a compliance record of the message and copies it to the mailbox of each participant, including guest and hybrid users (special cloud-only mailboxes are used for this purpose). With 250 participants in a group chat, that’s 250 copies of the same message. With 300, it’s 300, and so on.
The Office 365 infrastructure has lots of server resources available to do this work and store the messages, but it is wasteful. Group chats don’t have a mailbox, so they aren’t able to store a single compliance record for messages in the same way that’s possible for channel conversations. From a compliance perspective, it’s good that the messages are captured, but if you investigate a problem, the potential number of duplicate items that a content search or eDiscovery case might uncover is now much larger.
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