I use 1&1 for web hosting and occasionally log into the webmail interface from my desktop to check spam settings etc.
It works fine every time with Firefox but Omniweb just hangs on a screen saying "Please wait until the application is logged in... ". Interestingly, Safari does the same thing so I'm guessing it's a webkit thing? Anything you guys can do about it as it's pretty frustrating to have to launch an alternative browser for one site.
I've set up a temporary email account on there so you can see for yourself.
If you log in to webmail.1and1.co.uk with the account
omni@olpin.net and password
omnitest you should be able to see for yourself (though obviously you'll have to use firefox to check your mail ;) ).