Sender missing for domainless From: header after upgrade to 1.7.3

Prerequisites

• I have searched for duplicate or closed issues
• I can recreate the issue with all plugins disabled

Describe the issue

After upgrading Roundcube from v1.6.17 to v1.7.3, some locally generated system messages no longer show a sender in the message list.

The affected messages contain a domainless From: header, for example:

From: foo
To: [email protected]
Subject: Test

Example:

other e-mail clients, such as Thunderbird, are able to show those:

What browser(s) are you seeing the problem on?

Chrome, Firefox

What version of PHP are you using?

8.4

What version of Roundcube are you using?

v1.7.2

JavaScript errors

No response

PHP errors

No response