Question : DNS Setup

I have a dedicated windows server running IIS 6 with an SMTP server etc.. I want to send an email on behalf of a client (to an opt-in database - not spam) to their database of about 40,000 customers. Their domain is not hosted on my server...however, when I email from my server using their domain as the sender...should I place something in my DNS server so that reverse lookups work correctly... if so... how and what should i put in my DNS assuming the domain is:  www.xyz.com

I ask this, as I am currently not getting all the emails delivered to their customers...and this is a problem as you can imagine. I don't want to use a paid for email sending website either.

Answer : DNS Setup

The major companies have spent a lot of time speaking to the major providers to get on their white lists and establish the feedback loops. They will be sending out millions of emails a day, and will have constant communication with Yahoo, Hotmail and AOL etc to ensure the email gets delivered.

For the other providers, as long as there is a valid reverse DNS record, with matching DNS lookup and SMTP banner, the message should get through. If SPF records are set then those would need to be adjusted as well.
The PTR record does NOT have to match the domain the email is coming from.

If you want to see how these companies setup themselves up, sign up for an account and see what instructions are sent to you, or made available inside their admin tools. That will give you an idea what is required.

Simon.