I am working in a Market Research Company. As so, I have to send lots of email invitations to people to participate to online surveys. Those people agreed to give us their email address, and declared explicitely being available for research. I want to stress that it should not be considered as spam, although those emails might be harassing after a while.
In order to offer the best quality of service, we recently subscribed to a specific Internet DSL connection, with its ip addresses range, and I am sending the emails through the ISP's smtp server. However, as we want to be transparent and reachable, the sender's email address of these messages is an existent company address.
The company mail server, though, is on the other Internet connection (other ip addresses range). Also the company web and mail domain names are registered to this other Internet ip range.
One of the problems I encounter is the error
554 #5.5.4 Relaying denied. IP name lookup failed for [new ip]
To solve the problem, I read that I should assign a reverse DNS address. Could anyone suggest what entry I could safely have my ISP to add in its PTR database? Do I need to buy any new domain name, or should I assign a name matching the sender's email address? If I do assign a name matching the senders's email address, is it safe to do so for the day to day emailing of the company through the company mail server connected through the other ISP?
More generally speaking, I would be pleased to learn about the rules I should apply for this activity, in order to limit the stress for the people, the networks and the servers, and in order to be able to send as many emails as possible successfully?
Thank you for your help in advance.