Windows server 2008 SMTP service using for website

Question

I am working on .net applicaton that need to send emails to clients. I am trying to figure out what would be that best solution to send emails. Here is what i have considered. Could you please suggest what would be the best way to go for?

1>Windows server 2008 in built smtp
service.

2>Exchange server hosted in our
datacenter.

3>Use google apps for sending
emails(Basically same as gmail like
for custom domain).

I have explored all options and below are findings.

1>I think would be way to go. Also
supports drop in directory to send
emails so can achieve disconnected
email activity.

2>Application would be tied up with
availability of exchange server and
we dont have any exchange server
support personal. Only developers
poke around in exchange server and
got it working. So if option 1 is as
good as 2 then would like to go with 1. 
Is there any drop in directory feature in exchange server like 1?

3>Tried gmail smtp stuff didnt
work. I was receiving timeout error.
Also there is no guarantee that
gmail will send our mail
reliability. They can decide anytime
to stop sending our mails as we are
using free standard version of
google apps.

Other questions: I installed smtp service in windows server 2008. Now to use this do i need to change any MX record and anything? What i need to do so it can send email using my domain name. Or it can send email for any domain?

Answer 1

I would use a hybrid of 1 and 2. Use local SMTP, but have it relay to your exchange server. Emails will queue if it can't relay to exchange and you have one server(s) that handle all of your outgoing/incoming mail. This support doc explains this setup: http://support.microsoft.com/kb/303734

You only need an MX record if you'll be receiving mail from that domain too.

I would also put in a reverse DNS entry for your domain, which will help with spam detection.