I just upgraded my server from Debian 9 to Debian 10. Everything worked fine and is working fine with one exception. I can't connect via an external Mail application. Be it Mail on macOS or Outlook. Receiving and sending works fine via webmail. What could the problem be? Debian and ISPConfig are both up2date. I use dovecot. I also tried the Perfect Server Guide (https://www.howtoforge.com/perfect-server-debian-10-buster-apache-bind-dovecot-ispconfig-3-1/) again but to no avail. Edit: this is the output of htf_report.txt: ##### SERVER ##### IP-address (as per hostname): ***.***.***.*** [WARN] could not determine server's ip address by ifconfig [INFO] OS version is Debian GNU/Linux 10 (buster) [INFO] ISPConfig is installed. ##### ISPCONFIG ##### ISPConfig version is 3.1.15p3 ##### VERSION CHECK ##### [INFO] php (cli) version is 7.3.14-1~deb10u1 ##### PORT CHECK ##### ##### MAIL SERVER CHECK ##### ##### RUNNING SERVER PROCESSES ##### [INFO] I found the following web server(s): Apache 2 (PID 14884) [INFO] I found the following mail server(s): Postfix (PID 11488) [INFO] I found the following pop3 server(s): Dovecot (PID 11534) [INFO] I found the following imap server(s): Dovecot (PID 11534) [INFO] I found the following ftp server(s): PureFTP (PID 11650) ##### LISTENING PORTS ##### Server) () Local (Address) [anywhere]:110 (11534/dovecot) [anywhere]:143 (11534/dovecot) [anywhere]:465 (11488/master) ***.***.***.***:53 (11666/named) [localhost]:53 (11666/named) [anywhere]:21 (11650/pure-ftpd) [anywhere]:22 (1273/sshd) [localhost]:953 (11666/named) [anywhere]:25 (11488/master) [anywhere]:993 (11534/dovecot) [anywhere]:995 (11534/dovecot) [localhost]:10023 (960/postgrey) [localhost]:10024 (11521/amavisd-new) [localhost]:10025 (11488/master) [localhost]:10026 (11521/amavisd-new) [localhost]:10027 (11488/master) [anywhere]:587 (11488/master) [localhost]:11211 (1186/memcached) [localhost]10 (11534/dovecot) [localhost]43 (11534/dovecot) *:*:*:*::*:8080 (14884/apache2) *:*:*:*::*:80 (14884/apache2) *:*:*:*::*:8081 (14884/apache2) *:*:*:*::*:465 (11488/master) *:*:*:*::*:53 (11666/named) *:*:*:*::*:21 (11650/pure-ftpd) *:*:*:*::*:22 (1273/sshd) *:*:*:*::*:953 (11666/named) *:*:*:*::*:25 (11488/master) *:*:*:*::*:443 (14884/apache2) *:*:*:*::*:993 (11534/dovecot) *:*:*:*::*:995 (11534/dovecot) *:*:*:*::*:10024 (11521/amavisd-new) *:*:*:*::*:10026 (11521/amavisd-new) *:*:*:*::*:3306 (11255/mysqld) *:*:*:*::*:587 (11488/master) ##### IPTABLES ##### Chain INPUT (policy ACCEPT) target prot opt source destination f2b-postfix-sasl tcp -- [anywhere]/0 [anywhere]/0 multiport dports 25 Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain f2b-postfix-sasl (1 references) target prot opt source destination REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable REJECT all -- ***.***.***.*** [anywhere]/0 reject-with icmp-port-unreachable RETURN all -- [anywhere]/0 [anywhere]/0
I feel stupid... I fix the problem this was it: https://makeityourway.de/dovecot-2-3-couldnt-parse-dh-parameters/
