As per documentation, it seems there is a 1800 operations/3600 seconds rate limiting for sending messages. However, as I understand this, this only applies to 1:1 conversations? Does this mean that my API which sends 1 personal message to 3000 users (sequentially) will not be affected by this threshold? Thank you in advance!
Documentation: https://learn.microsoft.com/en-us/microsoftteams/platform/bots/how-to/rate-limit
As I am still in planning phase for this one, I am still trying to consider the possible limitations for the system.
In addition to the limitations Meghana has mentioned, you would also need to pay attention to the limits on the create conversations. If this is a first time you would be sending a message to a user, it might fall under Create Converstation category which has the following limitations again.