Outlook: Filter email by recipient/sender's domain (bug)

I was looking for a solution to filter emails handling with customer. I have stumbled upon an Outlook bug. I share here my learning and workaround.

First implementation: rule by recipient and sender's domain

I wanted to get my emails sent by a customer or to a customer marked with a special category.

For this I have used a combination of 2 rules:

With @<customerdomain> in the sender's address and

With @<customerdomain> in the recipient's address

Unfortunately, the second rule did not run if the recipient email was kind of resolved to its display name.

This looks like a mysterious bug mentioned also here. The question is unfortunately closed and without any proper answer.

Workaround: filter by header

My solution to workaround this issue, is to use a rule that filter the message header:

With @<customerdomain> in the message header.

This works properly and also is only one rule instead of 2.

Still it is a bit unexpected that the first approach did not work.

Workaround 2: with VBA

See this post how you can properly categorize Emails and Meetings automatically with VBA.