SMTP server for sending thousands of mail notification on daily basis

I'm in the process building a web application which is has a potential to send thousands of email on daily basis (most of it is system notification emails)

I'm using dedicated server for start but I'm thinking to use such as a smtp server to handle the sendmail process. Not just to reduce the server load but the most important thing is I don't wan't my server IP blacklisted in any spam list such as spamhaus.org

Can you suggest me what the best deal for this situation? Options that I have so far are :

• Using goggle app smtp with premier account. This is the option I prefered but I'm not sure whether google has such limitation that does not fit my situation
• Using commercial smtp server (If this the best option, can you suggest me any reliable service for this?)

I would recommend a commercial solution because then your taken out of the maintenance and if you do get blacklisted you can enlist their support team to take care of it.

I've used campaign monitor and had very good success with them. The rates are comparable and the interface is very easy to use. This is more of a small business solution.

I've also used Responsys and Yesmail. These are more enterprise solutions and might be a little overkill for what your looking for.