Receive mails from someone@MISSING_DOMAIN but other clients see it correctly and header is fine.

When I receive email from one specific coworker, I see the mail as received from “name@MISSING_DOMAIN” while when I look into the header, which looks fine by the way, is not in there.
Maybe a small hint, his name is “Someone Someone [Company]”. The square brackets, I mean.
Strictly, it might be possible that these characters are not allowed in a recipient’s name, but any other client allows it. On other clients, the name shows correctly and the domain name is parsed correctly.

Can you fix this issue?

Dirk.

Hi Dirk,
does this happen to only some senders or to all of them? Is this on all your email account or just a specific one? Could you resend a test .eml file to me that has this issue? (forward to rust@emclient.com)
Which version are you running (Help > About) ?

Best regards,
Olivia

The version is 6.0.23421.0
I will forward the email to you but I need to strip it down somewhat because of privacy reasons. Please handle it with care.

Of course, that why I asked if there is a harmless one you could resend or if you are able to replicate the issue with a test file.