Any problems with relay.plus.net at the mo?

[#1]

My email client on my Mac is spending ages trying to send mail via relay.plus.net and fails (reports server offline). Been working fine for over a year so not sure what's happening.
I can traceroute ok to the server and telnet in on port 25 (not that I know what to type after) so I'm sort of assuming the problem is mine but I'm short of ideas for a fix. Did it first yesterday, then worked again for awhile but I can't send emails again at the moment.
POP3 and incoming emails are fine.

[#2]

Hmm. If it was Windows I'd suggest antivirus, and will anyway (even though I know it's not really a widespread thing on Macs) - could that be it?
Otherwise I can only suggest the usual client checks - restart, reboot, recreate account etc?
There's nothing we're aware of issue wise at this end of things, I guess all the account settings are correct?

[#3]

Thanks for the feedback, I had a feeling it was only me
I've also now discovered where the problem is, it's the TG582n router. If I put my Billion 7800N on email goes fine, if I go back to the TG582n it fails. I should point out the TG582n has the demo firmware from the IPv6 trial forum link in it, I'll need to try again with that FW using default settings to check if any of the changes I've made, new DHCP pool, fixed DHCP IP allocations etc. have caused the problem.