Microsoft OAuth Fetching Mails are very slow

[HochzeitManagement]

We are experiencing significant issues with mailboxes that come from Microsoft Exchange OAuth. If I want to synchronize a folder with 10,000 emails, it takes forever.

How should we proceed?
We fetch 300 emails, and this usually takes about 30 seconds. Just for fetching.

Why is it so slow?
Are we doing something wrong here? Or is the connection just that slow?
With other providers, this is super fast.

Thanks for your help

[jstedfast]

If you enable protocol-logging by passing a ProtocolLogger with timestamps enabled to the ImapClient .ctor, does it show the response from the server taking a long time to send and/or each individual response taking a while? Or?

As you noted, MailKit is very fast with other servers, so it sounds like this is just a slow connection to Microsoft Exchange -or- it's just the server being slow to process requests.