Email has become an important part of maintaining relationships with clients. However, due to aggressive anti-spamming initiatives by internet service providers (ISPs)  mass emailing your clients may not work because the ISPs will block your email. When you are blocked your email does not get delivered and you can't communicate with your clients.

You can attempt to contact each ISP and request that they let your email thru and they may or may not do that. However nothing is forever and even if they let you mass email once, does not mean you won't be blocked the next time you try.

This has given rise to a new category of companies that specialize in email and newsletter delivery. These companies do more than provide email list management and nice newsletter formats. They also do the leg work for you in maintaining relationships with ISPs to ensure your mass emails don't get blocked.

None of this is fool proof, however if you are planning on emailing or sending newsletters to your clients on a regular basis and you have more than a few on your list, you might be well advised to retain the services of company specializing in handling your  email service. This should lead to fewer undelivered emails and newsletters and allow you to focus on the content of what you are sending and not spend time negotiating with a host of ISPs.