Since our ISP (German IONOS / 1&1) has reduced the error tolerance for email addresses to almost zero, I receive a lot of daily postmaster notifications from Mercury about delivery failures, as IONOS no longer accepts the incorrectly addressed mails and only returns an error "554 - Transaction failed". As an example, the following is very often entered into the To: field or automatically inserted: Doe, John < john.doe@example.com > john.doe@example.com < john.doe@example.com > john-paul doe < john.p.doe@example.com > If you simply put the plain name in inverted commas, everything would go through cleanly. But users don't do that. Often it is also due to the incorrectly configured mail client of the communication partner. What I'm getting at ... Other mail clients, such as Thunderbird, check and correct incorrect address entries automatically. Users who are connected to Mercury via Thunderbird almost never send any delivery failures to the postmaster. I wish Pegasus would also check and adjust incorrect address entries on its own. Translated with www.DeepL.com/Translator (free version)