Hey Fabio,
There are a few things to look at. This is going to depend on the application insisde of O365 that you are using.
For exchange, I would encourage you to look at this blog post - https://blogs.msdn.microsoft.com/exchangedev/2011/06/23/exchange-online-throttling-and-limits-faq/
You can run Get-Throttlingpolicy to see what the limits are (I think 20 is the connections limit by default).
For Proplus its a bit more complicated:
There is a 5 device limit that is associated with Office Pro Plus (as in only 5 different devices can be logged in per user). If a 6th logs in, it will error, or kick out an old stale one.
(https://support.office.com/en-us/article/understand-subscriptions-and-licenses-in-office-365-for-bus...)
You can see these by doing the following:
From any computer, go to https://portal.office.com/Account/#home and sign in using your work or school account, if prompted.
From the Install status tile, select Manage installs.
Under Install status, select Deactivate to deactivate the Office installs you no longer use.
For Azure/Microsoft Online, I do not know of a limit other than the application ones. I assume you meant either proplus or exchange online, so I included those, if it was something else let me know and I will see what I can find!
Adam
