[Evolution] Replies to emails with attachments take forever to open (EWS)

[Axel Lieber <axel progress biz>]

Hi everyone,

Ubuntu 20.04, Evolution EWS 3.36.4
Two mailboxes, one with an Exchange
Server, the other with Gmail. 

I've been using Evolution for a couple of weeks now and I'm generally
pleased. There's one problem that's quite annoying though. Replying to
emails that have attachments triggers a lengthy waiting process, up to
30 seconds. In other words, from the point when I click on the reply
button to the point where the reply email actually opens, can take that
long. With emails that do not have any attachments, the reply opens
within one or two seconds (still a little slow but bearable).

This problem only applies to the mailbox with the exchange server. It
doesn't happen with the Gmail account.

What can I do here?

Thanks for any advice. 

Axel