[gavinlew]

5 te4-1.telehouse-north.core.enta.net (87.127.236.38) 0.953 ms 0.922 ms 1.560 ms
6 194.74.65.57 (194.74.65.57) 1.079 ms 1.016 ms 0.884 ms
7 core2-pos14-0.ealing.ukcore.bt.net (62.6.201.85) 1.460 ms 1.806 ms 1.204 ms
8 core2-pos13-3.kingston.ukcore.bt.net (62.6.201.102) 2.153 ms 2.057 ms 2.185 ms
9 interconnect2-gig1-0.kingston.fixed.bt.net (194.72.3.5) 2.115 ms 2.977 ms 3.247 ms
10 ftip002956817.kingston.fixed.bt.net (62.7.100.242) 11.469 ms 11.439 ms 11.717 ms
11 195.99.173.212 (195.99.173.212) 38.591 ms * *

Trace from telehouse london to your VPOP3 server , I would suggest the problem is connectivity based.

also ;

[gavinl@ ]$ telnet 195.99.173.212 5108
Trying 195.99.173.212...

And finally nmap scanning fails as equipment unreachable

Hope this helps.