Auctiva is the most widely known for such things - I do know that many, various emails can be automated with them, but I've never used them so I don't know if you can customise emails to go out for different items (usually with things like this, you just get one email template that's triggered for every purchase, and use codes to auto-fill relevant details to specific buyers, so they look personalised but actually aren't).
Your best bet would probably be to look for a community forum for a site like Auctiva to confirm features, and/or see if anyone can point you in the right direction (on the presumption that users of that kind of software have done a bit more research of available programs and options).
