Ubuntu server 18.04 ISPConfig 3.1.12 (recently migrated from version 188.8.131.52p9) This morning I set up a Client Circle consisting of all active clients and resellers. I then sent a message to that Client Circle using the control panel 'Send customer information/Send email message to clients and resellers' form; I used my own email address ([email protected]) as the sender address, an address which naturally is authorized to send mail on the server. Everything seemed to work successfully, but the messages have not been delivered. I have checked /var/log/mail.err (empty) and /var/log/mail.log, where I could not find any relevant entries. The normal mail system is working fine. Please help me to solve this problem; it's rather urgent (of course I can if necessary send the message manually, though that means collecting the email addresses).