[shadow-tech]

that is a good question. in short i dont know.

but keep this in mind:

some ISPs will block you for 15 minutes if you check your email too often. i dont mean too many times in a day, but if you press send/receive to quickly, (i.e. send/receive...send/receive...send/receive...send/receive...send/receive...), they will think your a spammer or something and block you for 15 mins or so.

2 minutes should be ok but i wouldn't go anything less then that.

hope this info is somewhat useful.