I stopped using Incredimail a while ago, to start with it was a very good program and I could send what I considered at the time to be unique looking e-mails.
The only price I had to pay was to have a little link at the bottom of the message to promote the software.
I stopped using it when that little discreet message was replaced by a banner to Thunderbird instead. Also for some reason Incredimail stopped working with my e-mail account on my system.
Thunderbird doesn't have the notifier and all the little touches (possibly does with a plug-in somewhere I haven't looked) but it's nice to send e-mails again with just what I wrote as the contents.