One of the following errors appear while trying to send an email to Plesk mail server or from Plesk mail server to an external mail server:
The following error can be found in
postfix/smtp: E3B24978700: to=<email@example.com>, relay=none, delay=537, delays=446/0.02/91/0, dsn=4.4.1, status=deferred (connect to alt2.gmail-smtp-in.l.google.com[10.10.10.10]:25: Connection timed out)
postfix/smtp: connect to external.ms[10.10.10.10]:25: Connection timed out
It is possible to send an email from outside the server to the server
When trying to connect to port 25,
No route to host is returned:
# telnet mta5.am0.yahoodns.net 25
telnet: connect to address 184.108.40.206: No route to host
telnet: connect to address 220.127.116.11: No route to host
telnet: Unable to connect to remote host: No route to host
# telnet alt2.gmail-smtp-in.l.google.com 25
telnet: connect to address 18.104.22.168: No route to host
telnet: connect to address 2607:f8b0:4002:c03::1b: Network is unreachable
telnet: Unable to connect to remote host: Network is unreachable
25 port is shown as filtered:
# nmap -p 25 mta5.am0.yahoodns.net
Starting Nmap 6.40 ( http://nmap.org ) at 2016-10-30 21:29 CET
Nmap scan report for mta5.am0.yahoodns.net (22.214.171.124)
Host is up (0.12s latency).
Other addresses for mta5.am0.yahoodns.net (not scanned): 126.96.36.199 188.8.131.52 184.108.40.206 220.127.116.11 18.104.22.168 22.214.171.124 126.96.36.199
rDNS record for 188.8.131.52: mta-v3.mail.vip.ne1.yahoo.com
PORT STATE SERVICE
25/tcp filtered smtp
Connection issues with SMTP server.
Make sure that correct IP address and port number combination are used for the SMTP server in mail client preferences.
If the domain name is used instead of the mail server IP address, make sure that the domain is resolved to correct IP address:
#213912165 Error when trying to open website: "The page cannot be displayed"
- Make sure Plesk SMTP service is running on the server:
#213414669 How can I check that SMTP Plesk service is running OK on the server?
- Check the firewall settings (to get list of all ports used by Plesk see article:
#213932745 Which ports need to be opened for all Plesk services to work with a firewall?
Ultimately, stop any firewall running on the Plesk server and try to send an e-mail again. If this does not work, then the SMTP port is blocked from somewhere else in network. Contact your ISP for assistance.