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 <info(a)brand-acad.de&gt;: Host or domain name not found. Name service error for name=brand-acad.de type=AAAA: Host not found <georg.hellmann(a)akkon-hochschule.de&gt;: host mx2.johanniter.de[87.190.39.211] said: 550 #5.1.0 Address rejected. (in reply to RCPT TO command) <info(a)hochschule-calw.de&gt;: host mail3.srh.de[85.115.20.189] said: 554 5.7.1 Access denied (in reply to RCPT TO command) <julian.bomert(a)duw-berlin.de&gt;: host w014c3c8.kasserver.com[85.13.128.194] said: 554 5.7.1 <julian.bomert(a)duw-berlin.de&gt;: Relay access denied (in reply to RCPT TO command) <rektor(a)hs-hatz.de&gt;: Host or domain name not found. Name service error for name=hs-hatz.de type=AAAA: Host not found <wolfgang.schuster(a)hwtk.de&gt;: host hwtk-de.mail.protection.outlook.com[104.47.11.74] said: 550 5.4.1 Recipient address rejected: Access denied. AS(201806281) [DB5EUR02FT043.eop-EUR02.prod.protection.outlook.com 2023-06-13T20:09:27.312Z 08DB64B7D3DAB68D] (in reply to RCPT TO command) <martin.fritz(a)merz-akademie.de&gt;: host merzakademie-de01b.mail.protection.outlook.com[104.47.51.138] said: 550 5.4.1 Recipient address rejected: Access denied. AS(201806281) [DBAEUR03FT023.eop-EUR03.prod.protection.outlook.com 2023-06-13T20:09:27.404Z 08DB6B65DA18603C] (in reply to RCPT TO command) <physiksprecher(a)physik.rwth-aachen.de&gt;: host mx1.rz.rwth-aachen.de[137.226.78.57] said: 550 #5.1.0 Address rejected. (in reply to RCPT TO command) <w.hahn(a)praxishochschule.de&gt;: host praxishochschule-de.mail.protection.outlook.com[104.47.51.202] said: 550 5.4.1 Recipient address rejected: Access denied. AS(201806281) [AM7EUR03FT028.eop-EUR03.prod.protection.outlook.com 2023-06-13T20:09:29.219Z 08DB6BCB4DBFDDE9] (in reply to RCPT TO command) <eva.schwinghammer(a)provadis-hochschule.de&gt;: host provadishochschule-de02b.mail.protection.outlook.com[52.101.68.3] said: 550 5.4.1 Recipient address rejected: Access denied. [DU2PEPF0001E9C0.eurprd03.prod.outlook.com 2023-06-13T20:09:29.538Z 08DB6BE5BB9C44E4] (in reply to RCPT TO command) <martin.reckenfelderbaeumer(a)allensbach-hochschule.de&gt;: host post.allensbach-hochschule.de[85.209.203.4] said: 550 5.1.1 <martin.reckenfelderbaeumer(a)allensbach-hochschule.de&gt;: Recipient address rejected: User unknown in virtual mailbox table (in reply to RCPT TO command) <rektor(a)htwsaar.de&gt;: host m-relay.htw-saarland.de[134.96.7.233] said: 550 5.1.1 <rektor(a)htwsaar.de&gt;: Recipient address rejected: undeliverable address: Recipient address lookup failed (in reply to RCPT TO command) <afeld(a)uni-postdam.de&gt;: Host or domain name not found. Name service error for name=uni-postdam.de type=AAAA: Host found but no data record of requested type <karbach(a)uni-wupperatl.de&gt;: Host or domain name not found. Name service error for name=uni-wupperatl.de type=AAAA: Host not found <Rektor(a)fh-stralsund.de&gt;: host a1871.mx.srv.dfn.de[194.95.232.132] said: 550 5.1.1 <Rektor(a)fh-stralsund.de&gt;: Recipient address rejected: undeliverable address: host mx.fh-stralsund.de[194.94.72.35] said: 550 5.1.1 <Rektor(a)fh-stralsund.de&gt;: Recipient address rejected: User unknown in virtual mailbox table (in reply to RCPT TO command) (in reply to RCPT TO command) <insa.sjurts(a)zu.de&gt;: host zu-de.mail.protection.outlook.com[104.47.51.138] said: 550 5.4.1 Recipient address rejected: Access denied. AS(201806281) [DBAEUR03FT003.eop-EUR03.prod.protection.outlook.com 2023-06-13T20:09:35.554Z 08DB6C493B1A10A8] (in reply to RCPT TO command) <jan.wierig(a)ovgu.de&gt;: host a2501.mx.srv.dfn.de[194.95.233.9] said: 550 5.1.1 <jan.wierig(a)ovgu.de&gt;: Recipient address rejected: undeliverable address: host mx3.ovgu.de[141.44.1.69] said: 550 5.1.1 <jan.wierig(a)ovgu.de&gt;: Recipient address rejected: User unknown in virtual alias table (in reply to RCPT TO command) (in reply to RCPT TO command) <praesidentin(a)uni-koblenz-landau.de&gt;: host nsmtp.uni-koblenz.de[141.26.64.14] said: 550 5.1.1 <praesidentin(a)uni-koblenz-landau.de&gt;: Recipient address rejected: User unknown in virtual alias table (in reply to RCPT TO command) <juerge.deicke(a)wb-fernstudium.de&gt;: host mail.sgd.de[213.157.13.165] said: 550 Address unknown (in reply to RCPT TO command) <Eric.Runge(a)TU-Ilmenau.de&gt;: host a2221.mx.srv.dfn.de[194.95.232.182] said: 550 5.1.1 <Eric.Runge(a)TU-Ilmenau.de&gt;: Recipient address rejected: undeliverable address: host piggy2.rz.tu-ilmenau.de[141.24.186.70] said: 550 5.1.1 <Eric.Runge(a)TU-Ilmenau.de&gt;: Recipient address rejected: User unknown in relay recipient table (in reply to RCPT TO command) (in reply to RCPT TO command) <praesident(a)uni-vechta.de&gt;: host c1181.mx.srv.dfn.de[194.95.238.54] said: 550 5.1.1 <praesident(a)uni-vechta.de&gt;: Recipient address rejected: undeliverable address: host smtpss.uni-vechta.de[131.173.80.250] said: 550 5.1.1 0 RESOLVER.ADR.RecipientNotFound; Recipient not found by SMTP address lookup (in reply to RCPT TO command) (in reply to RCPT TO command) <katja.rade(a)srh.de&gt;: host mx-74021879.mail.eu.retarus.com[94.199.89.39] said: 550 5.2.0 mailbox unavailable. (in reply to RCPT TO command)