If you use email to communicate with large groups of customers or subscribers, it is a good idea to be familiar with the bulk email sender guidelines of ISPs. Life is so much easier when you have bulk sending resources at your fingertips.
Understanding the bulk email sender guidelines, feedback loops (FBL) and blacklist or blocklist removal procedures of ISPs makes managing your email delivery and sender reputation so much easier.
Below, please find some useful links to bulk email sender guidelines and resources for some of the major ISPs.
It is always a better idea to work with ISPs rather than against them. The more you understand about bulk email sender guidelines, policies and requirements of your ISP and the ISPs of your recipients, the easier it will be to get your email delivered to the inbox of your recipients. Of course, it is not always easy to get a quick answer from a large ISP; so the resources above will make things a little easier for you.