Intermittent email problems

[#1]

For some weeks we have been getting intermittent error messages such as:
The connection to the server has failed. Account: '***', Server: 'mail.plus.net', Protocol: POP3, Port: 110, Secure(SSL): No, Socket Error: 10060, Error Number: 0x800CCC0E
The connection to the server has failed. Account: '***', Server: 'relay.plus.net', Protocol: SMTP, Port: 25, Secure(SSL): No, Socket Error: 10060, Error Number: 0x800CCC0E
The host 'mail.plus.net' could not be found. Please verify that you have entered the server name correctly. Account: '***', Server: 'mail.plus.net', Protocol: POP3, Port: 110, Secure(SSL): No, Socket Error: 11001, Error Number: 0x800CCC0D
This has occurred on both my PC (running Outlook) and on my wife's (running Outlook Express) so it doesn't seem to be a problem with corrupted client or TCP/IP. I have tried restarting Outlook/OE, and deleting and reentering the accounts, and this usually works - for a while - but then the problem can return at any time. 
The PCs are networked on an SMC hub NAT router and I have checked settings there and can't see anything wrong. There is no other firewall, and I have tried turning off AVG email scanner without effect. There don't seem to be service problems causing it. I have checked all passwords and I can Telnet to mail.plus.net without problems.  Can anyone help?

[#2]

A number (including myself) have seen these sort of problems, thankfully I've only had it 2 or 3 times, whether it's due to packet drops on the network or servers unavailable I'm not sure, but I doubt it's anything to do with your setup.

[#3]

It's definitely not going to be the result of packet drops and I'd question the assumption that it's nothing to do with Mike's setup. As far as we're concerned there are no problems with routing to the mail platform. Some people have been complaining of what looks like isolated DNS issues that I guess could be related.
To rule out DNS I guess you could try changing the server name you're using from 'mail.plus.net' to '212.159.8.81'. Try that temporarily and see how you get on (although I'd make sure you change it back after a week or so).

[#4]

I didn't say "it had nothing to do with his setup" - I said "I doubt it's anything to do with your setup"  Slightly different meaning, 'doubt' implying there was still a possibility even though IMHO it was unlikely - invierw of all the other posts of a similar nature.
Isthe ip 212.159.8.81 for mail.plus.net likely to change then?

[#5]

Quote from: Anotherone

Isthe ip 212.159.8.81 for mail.plus.net likely to change then?

I've know it to change several times during my time with Plusnet so it's possible.