MN wrote:

My question is about how an utf-8 encoded message is handled.
In one case, the import from a folder in exchange messages get corrupted.
When using the POP3 an utf-8 encoded messages arrives without any corruption

And just what does "corruption" mean? What do you see? What did you expect
to see? Is part of the e-mail missing? What?

So what did the Exchange admin say about this "corruption" of e-mail content
delivered to your Exchange mailbox?