This is the mail system at host mail.zapf.in. I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message. The mail system <clemens.schlage(a)asta-hamburg.de&gt;: Host or domain name not found. Name service error for name=asta-hamburg.de type=AAAA: Host not found <info(a)fsan-fhl.de&gt;: Host or domain name not found. Name service error for name=fsan-fhl.de type=AAAA: Host not found <fachschaft-10(a)googlegroups.com&gt;: host gmr-smtp-in.l.google.com[142.250.110.14] said: 550-5.1.1 The email account that you tried to reach does not exist. Please try 550-5.1.1 double-checking the recipient's email address for typos or 550-5.1.1 unnecessary spaces. Learn more at 550 5.1.1 https://support.google.com/mail/?p=NoSuchUser l21-20020a2e99d5000000b002b6f8d5f93csi431768ljj.2 - gsmtp (in reply to RCPT TO command) <asta.info(a)kiho-wuppertal.de&gt;: host mx00.ionos.de[212.227.15.41] said: 550 Requested action not taken: mailbox unavailable (in reply to RCPT TO command) <asta_hfm(a)hfm-berlin.de&gt;: host mx1.in-berlin.de[192.109.42.28] said: 554 5.7.1 no such user (in reply to RCPT TO command) <asta(a)ostfalia.de&gt;: host mx2.sonia.de[141.41.1.238] said: 550 5.1.1 <asta(a)ostfalia.de&gt;: Recipient address rejected: User unknown in relay recipient table (in reply to RCPT TO command) <david.weiler(a)stud.ph-gmuend.de&gt;: host mx1.belwue.de[129.143.76.2] said: 577 5.1.1 <david.weiler(a)stud.ph-gmuend.de&gt;: Recipient address rejected: undeliverable address: host mail-hub02.belwue.de[129.143.76.42] said: 577 5.1.1 <david.weiler(a)stud.ph-gmuend.de&gt;: Recipient address rejected: undeliverable address: host mta-in-vm.ph-freiburg.de[193.197.136.98] said: 550 5.1.1 <david.weiler(a)stud.ph-gmuend.de&gt;: Recipient address rejected: User unknown in relay recipient table (in reply to RCPT TO command) (in reply to RCPT TO command) (in reply to RCPT TO command) <lak-hh(a)asta.haw-hamburg.de&gt;: host c2601.mx.srv.dfn.de[194.95.239.27] said: 550 5.1.1 <lak-hh(a)asta.haw-hamburg.de&gt;: Recipient address rejected: undeliverable address: host mailgate.asta.haw-hamburg.de[141.22.212.2] said: 550 5.1.1 <lak-hh(a)asta.haw-hamburg.de&gt;: Recipient address rejected: User unknown in virtual mailbox table (in reply to RCPT TO command) (in reply to RCPT TO command) <studentensprecher(a)thhf.net&gt;: host mail.stud.thh-friedensau.de[195.37.84.65] said: 550 Relay not permitted (in reply to RCPT TO command) <PersonalratTuV(a)uni-koeln.de&gt;: host seraph.rrz.uni-koeln.de[134.95.19.134] said: 550 #5.1.0 Address rejected. (in reply to RCPT TO command) <Studierendenvertretung.LMZ(a)phil.uni-augsburg.de&gt;: host a2541.mx.srv.dfn.de[194.95.233.14] said: 550 5.1.1 <Studierendenvertretung.LMZ(a)phil.uni-augsburg.de&gt;: Recipient address rejected: undeliverable address: host caudle.rz.uni-augsburg.de[137.250.2.146] said: 550 unknown recipient (in reply to RCPT TO command) (in reply to RCPT TO command) <shk-vertretung(a)uni-due.de&gt;: host mx-serv5.uni-due.de[134.91.50.6] said: 500 5.7.1 <shk-vertretung(a)uni-due.de&gt;: Recipient address rejected: access-recipient: Empfaenger:in derzeit nicht erreichbar. Recipient temporarily not reachable. (in reply to RCPT TO command) <fsil(a)uni-hildesheim.de&gt;: host robin.uni-hildesheim.de[147.172.16.6] said: 550 Invalid Recipient 6 (in reply to RCPT TO command)