The original message was received at Sat, 14 May 2022 14:47:34 +0200 (CEST) from btr0xj [132.180.8.25] ----- The following addresses had permanent fatal errors ----- <charlotte1.geiger(a)uni-bayreuth.de&gt; (reason: 550 5.1.1 <charlotte1.geiger(a)uni-bayreuth.de&gt;... User unknown) ----- Transcript of session follows ----- ... while talking to [127.128.8.11]: <<< 550 5.1.1 <charlotte1.geiger(a)uni-bayreuth.de&gt;... User unknown 550 5.1.1 <charlotte1.geiger(a)uni-bayreuth.de&gt;... User unknown <<< 503 5.0.0 Need RCPT (recipient)