The symptoms are simple - if a connection is not made to a server in about 6 seconds (POP3 or IMAP easy to see, becuase you se "loggin on"), then it takes exactly 3 minutes to connect.
Most users have given up by then, but I alwsy wait - and finally get a connection. It appears very common where there are multiple cell sites in range, and also at peak usage times.
Vodafone have addressed some areas, and it gets better, and may be fine for a week, and then back it comes. I've tried a wide range of devics - iMATE, HP iPAQ 6365, Connect Card, Bluetooth via mobile phone, Smartphone and they all suffer the same problem.
And it's not just mail servers.