mails unreadable

Hi all,

There is a very rare experience on getting emails specially from 1-2 senders. All the emails from them become unreadable. Sure that it is not font issue, because there is no format on the emails. This happened on the Mail of macOS and iOS too. But the emails can be read properly by other mail clients like Thunderbird or on webmail.

My email account is "Exchange". Not sure if it is related.

Thanks.