Apple mail stopped sending email

I have been using mail as my email client on my mac pro desktop (Osx10.6 Snow Leopard - Mail4.6)to access and send emails from my @ntlworld.com account for several years. There have been odd incidences in the past where Mail app stop sending and receiving, which I had been able to resolve previously. On Friday night though I was unable to send mails out but was still receiving them. After attempting to resolve this for hours on end on Saturday, I eventually contacted Virgin my provider (who were previously NTL in another life). The upshot of this tragedy of an encounter was that they lost ALL the details of my previous emails by reformatting the Mail account after gaining access to my computer - despite telling them I expressly did not want to lose my data and them giving me feeble assurances that this would not occur - what's worse, is I now believe the problem was actually caused by them making changes to the pop and imap settings at their end, which of course would not comply with the previous ones set in preferences on my computer in my Mail application. I have now been forced to abandon Mail all together which I liked because of its simplicity, and use Thunderbird as a working alternative though I have to say I find it a little over complicated and quite ugly. Another downside to this is that attachments which would previoudly display on emails in the Mail app are now hidden in thunderbird which I do not like at all.