When entering POP3 details I get the error "Connection timed out"
"Connection timed out" could mean a lot of things, but it's often caused by the wrong POP3 port or a firewall on the server (or ISP) blocking access to the port.
If you have console access on the server, try doing a manual connection to rule things out (in this example, 'localhost' is the name of the POP3 server):
# telnet localhost 110 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. +OK POP3 server ready. QUIT Connection closed by foreign host.
If you can't get the connection to open at all, you need to make sure you're trying to connect to the right host and port. If you're certain, there is possibly a firewall blocking incoming or outbound traffic on your POP3 port (usually 110).
If your server is on a residential internet account (e.g, DSL), oftentimes outbound connections on port 25 will be blocked unless you use the ISPs SMTP server. In these situations it's fine to use your ISP's SMTP (outgoing) and your own POP3/IMAP (incoming).
If you need to use SSL to connect (for example, if you're using GMail), you'll need to use openssl to attempt a connection on port 995, as telnet will not work:
# openssl s_client -connect pop.gmail.com:995 -quiet depth=1 C = US, O = Google Inc, CN = Google Internet Authority verify error:num=20:unable to get local issuer certificate verify return:0 +OK Gpop ready for requests from 127.0.0.1 mx4pf9618614pbc.17
If you're not able to connect, you'll need to double-check that outbound connections to port 995 are allowed within your network.