MC259845 – Updated June 16, 2021: Microsoft has updated the message below to clarify this impacts Win32 and Win64 clients. Thank you for your patience.
Microsoft is making some changes to limit the number of individual recipients allowed for scheduling a Teams meeting from Outlook (Win32 and Win64 client only at this time). Microsoft will apply this limit for meetings created with more than 750 recipients in the invite. This limit does not apply to the content of Distribution Lists and therefore Microsoft encourages users to use Distribution Lists when inviting a large number of attendees to a Teams meeting.
When will this happen:
Microsoft will roll-out this change beginning in late June and expect to complete by late August.
How this will affect your organization:
Users using Outlook (Win32 and Win64) will see an error message dialog when trying to schedule or reschedule a meeting with a number of attendees larger than the new 750 recipient limit and will be required to reduce the number of recipients or user Distribution Lists to send the meeting invite.
What you can do to prepare:
You may consider updating your training and documentation as appropriate.