- Plesk for Linux
One of the following errors appear while trying to send an email 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
qmail: 1491974064.856278 delivery 8214: deferral: Sorry,_I_wasn't_able_to_establish_an_SMTP_connection._(#4.4.1)/
It is possible to send an email from outside to the server.
When trying to connect to port 25,
No route to host
# telnet mta5.am0.yahoodns.net 25
telnet: connect to address 22.214.171.124: No route to host
telnet: connect to address 126.96.36.199: 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 188.8.131.52: 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 (184.108.40.206)
Host is up (0.12s latency).
Other addresses for mta5.am0.yahoodns.net (not scanned): 220.127.116.11 18.104.22.168 22.214.171.124 126.96.36.199 188.8.131.52 184.108.40.206 220.127.116.11
rDNS record for 18.104.22.168: mta-v3.mail.vip.ne1.yahoo.com
PORT STATE SERVICE
25/tcp filtered smtp
Traceroute to port 25 shows the following:
[root@server ~]# traceroute -T -p 25 gmail-smtp-in.l.google.com
traceroute to gmail-smtp-in.l.google.com (22.214.171.124), 30 hops max, 60 byte packets
1 example.com (203.0.113.2) 0.055 ms 0.015 ms 0.012 ms
2 example2.com (203.0.113.3) 0.181 ms example2.com (203.0.113.4) 0.170 ms example2.com (203.0.113.5) 0.168 ms
3 example3.com (203.0.113.5) 0.925 ms 1.105 ms example3.com (203.0.113.6) 1.380 ms
4 * * *
5 * * *
6 * * *
7 * * *
8 * * *
Remote SMTP server connectivity issues.
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 can be resolved into correct IP address .
- Make sure Plesk SMTP service is running on the server
- Check the firewall settings
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 or network administrator for assistance.