We have collected email addresses on our flu shot reminder cards which patients, but have never used them. We were thinking of using them this year to send a mass reminder email.
Sanofi Pasteur has a "First-2-Know" free service where you upload an Excel spreadsheet and I believe it will send the email for you. I haven't logged on to it yet to check it out.
For people that do send bulk emails I was wondering how you do it and if you like the method you are using.