How do I check to see if ports 25 [pop] and 110 [smtp] are open and listening? Suddenly have no email connectivity on my machine -- Thunderbird times out trying to connect to the ISP email server. Clueless ISP couldn't help.

thx

If you have root access to the pop/smtp server, run "netstat -tlpn" and check if the ports 25 and 110 are listed in the netstat output.

If you don't have access, (the server are in a ISP or whatever) you can use a network scanner like nmap: "nmap -p 25,110 ip_email_server".

Last I checked, netstat does not require privileged access to run.

when I run netstat -lnp as a normal user, it returns everything except PID/Program name (as root, it returns everything). I'm using Debian, may be other distros are different.

Ok, good to know.

...yes, the netstat's "program listing" option requires root access
anyway, did you figure out why you don't get your e-mails ?
if netstat shows the ports in listing state and the associated programs are fine, but the nmap does not shown the ports 25 and 110 in open state, then a firewall may be the problem. This firewall could be between the 2 machines or even running on the e-mail server.

Got the email to send and receive again by using the network assistant to stop then restart the network.

But shouldn;t netstat show the ports 25 and 110?

Output of netstat as root [ FYI: same output as user ] :

root@1[nuvu]# netstat -tlpn
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:2208 0.0.0.0:* LISTEN 4169/hpiod
tcp 0 0 0.0.0.0:139 0.0.0.0:* LISTEN 4285/smbd
tcp 0 0 0.0.0.0:631 0.0.0.0:* LISTEN 28501/cupsd
tcp 0 0 0.0.0.0:445 0.0.0.0:* LISTEN 4285/smbd
tcp 0 0 127.0.0.1:2207 0.0.0.0:* LISTEN 4186/python
tcp6 0 0 :::631 :::* LISTEN 28501/cupsd
tcp6 0 0 ::1:4539 :::* LISTEN 6103/java
tcp6 0 0 :::24444 :::* LISTEN 6103/java

thanks for the help!

The ports must be showed as open on the machine where the e-mail server is running, not at client machine.

Is "nuvu" the SMTP/POP server or just a workstation where you are reading/sending e-mails ? If it is just a workstation, a client, then there is no SMTP/POP programs running as servers.

nuvu is a directory on my workstation. What would I use to find out what ports are open on a workstation not acting as server?

I´m sorry, I missed your last post....

netstat is the program to inspect what ports are open in your computer as you did in a previous post.
When your computer start a conetion with a remove server on port 25 to send e-mails or to ports 110/143 to get e-mail using POP/IMAP protocols, it uses a temporary, randomic local port. Your firewall keeps tracks of this port and when the server answer to that port the firewall allows the communication, even this local port is not configured in anywhere.

Are you behinf a wireless router, or another firewall ?
May be other device is blocking you.....