Help Can't send email

[Zaichik]

I use the default mail ap to manage my email and I've set my accounts up on IMAP using the login, security and port settings on my email provider's (Virgin Media) website. However, although I can receive emails OK, it almost always refuses to send email when I use my Desire. I usually end up having to use my gmail account, which works fine - I don't really want to use that address, however.

The problem has been worse since the upgrade to 2.2 (unbranded Desire).

Can anyone help with this problem? My mobile provider is also Virgin, so I'm surprised it doesn't work properly.