I met a strange problem: cyrus-imapd service stopped for unknown reason and I could not receive emails. Even I restarted the service:
service cyrus-imapd start
I still could not receive emails. Telneting to the mail server showed the port was not open.
netstat -antp|grep 995
tcp 0 0 :::995 :::* LISTEN 30491/cyrus-master
netstat says cyrus-master only listens on ipv6 address. On the mail server,
telnet ::1 995
Trying ::1…
Connected to ::1.
Escape character is ‘^]’.
telnet command connects to ipv6 local address ::1 and shows cyrus-master works normally for ipv6 address on port 995.
netstat -anp|grep 995
tcp 0 0 :::995 :::* LISTEN 30491/cyrus-master
udp 0 0 0.0.0.0:995 0.0.0.0:* 661/portreserve
This command shows portreserve occupies port 995 for ipv4 address. Now stop the portreserve service
service portreserve stop
And restart cyrus-imapd service
service cyrus-imapd restart
This time, cyrus-imapd listens on port 995 for both ipv4 and ipv6 addresses:
netstat -antp|grep 995
tcp 0 0 0.0.0.0:995 0.0.0.0:* LISTEN 32330/cyrus-master
tcp 0 0 :::995 :::* LISTEN 32330/cyrus-master
It is interesting that portreserve only occupies udp port 995 for ipv4 address, why cyrus-master can not use tcp port 995 for ipv4 address? This might be a bug of cyrus-imapd.
Now everything is ok and I can receive my emails.
