I have mailbox on server (configured from tutorial perfect server for Ubuntu 16.04 with apache2 etc). After sending email to particular user from domains: 1) gle.com 2) lotusbb.abus.de 3) sassieditore.it I have errors like below: 1) X-Postfix; connect to gle.com[69.172.201.153]:25: Connection timed out 2) host lotusbb.abus.de[62.153.75.197] said: 550 Requested action not taken: mailbox unavailable (in reply to RCPT TO command) 3) 450 4.7.1 Client host rejected: cannot find your reverse hostname, [IP-address-of-my-server] About 1st point I tried telnet to localhost: Code: root@s1:~# telnet localhost 25 Trying 127.0.0.1... Connected to s1.example.com. Escape character is '^]'. 220 serwer-1.localdomain ESMTP Postfix (Ubuntu) ehlo localhost 250-serwer-1.localdomain 250-PIPELINING 250-SIZE 250-VRFY 250-ETRN 250-STARTTLS 250-AUTH PLAIN LOGIN 250-AUTH=PLAIN LOGIN 250-ENHANCEDSTATUSCODES 250-8BITMIME 250 DSN and I tried telnet to IP of domain gle.com: Code: root@s1:~# telnet gle.com 25 Trying 69.172.201.153... telnet: Unable to connect to remote host: Connection timed out Does it mean that postfix is not configured for relay on 25 port of smtp? Or maybe firewall block something? Code: root@s1:~# ufw status Status: inactive Code: root@s1:~# iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination f2b-dovecot-pop3imap tcp -- anywhere anywhere multiport dports pop3,pop3s,imap2,imaps f2b-pureftpd tcp -- anywhere anywhere multiport dports ftp f2b-postfix-sasl tcp -- anywhere anywhere multiport dports smtp f2b-sshd tcp -- anywhere anywhere multiport dports ssh Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain f2b-dovecot-pop3imap (1 references) target prot opt source destination RETURN all -- anywhere anywhere Chain f2b-postfix-sasl (1 references) target prot opt source destination RETURN all -- anywhere anywhere Chain f2b-pureftpd (1 references) target prot opt source destination RETURN all -- anywhere anywhere Chain f2b-sshd (1 references) target prot opt source destination RETURN all -- anywhere anywhere
