Entra App imap connection throttling if too often called?

Question

Hi everyone,

I’m connecting to an office365 mailbox to process emails via Oauth2 and a registered app in Entra with ImapAllAccess.

In the dotnet app I use a library (Mailkit) which helps me to connect, authenticate and open a folder (in my use case the Inbox),

This worked fine for many months, even when there are 2k mails in the mailbox.

Since this Sunday (2024-05-12) reading a message takes sometimes >20s.

Before the weekend reading 2k mails took just a few seconds.

Because of the long wait time the mail client connection time out. On some occasions I received a “Request throttled”.

There is some old question from 2021 with very similar issue but with an old outlook mailbox. I am wondering if there are any new updates and guidelines when using Office365 / Entra.

So what I am wondering, is there some kind of throttling when an app too often fetching mails via IMAP?

Or are there any recent changes in the system which I missed?