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 <rektor(a)uni-due.de&gt;: host mx-serv3.uni-due.de[134.91.50.6] said: 500 5.7.1 <rektor(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) <insa.sjurts(a)zu.de&gt;: host zu-de.mail.protection.outlook.com[52.101.73.21] said: 550 5.4.1 Recipient address rejected: Access denied. [AM2PEPF0001C70A.eurprd05.prod.outlook.com 2024-01-08T10:15:17.869Z 08DC0E9AAC014669] (in reply to RCPT TO command) <praesidialrat(a)ebs.edu&gt;: host mx-74021879.mail.eu.retarus.com[94.199.92.130] said: 550 5.2.0 mailbox unavailable. (in reply to RCPT TO command)