Mail problems

Hi

After changing to new mail server (one.com) where I have my webhotel, I've had strange problems with "Mail". Sometimes it shows new mails as read or at least it does it after about 5 minutes. Sometimes, after being in sleep mode, it won't take in new mails untill I've restarted it.

I've talked with one.com, they say that it is not their server. I think that is correct because I don't have these problems on my laptop.

I've installed Thunderbird and used that instead, but the problem is there too, even though I've set Thunderbird NOT to show unread messages as read!

I can't find taht option in "Mail".

I've deleted "Mail" from my iMac and copied the one I have on my laptop. That is an older version so I've had to upgrade OS 10.6.6 to 10.6.8 which I just did.

But the problem is still there.

Are there any preferences I can delete that might help?

But still, it is very strange that these things happens using both Mail and Thunderbird.

Any suggestions??

Henrik