I am creating a marketing company and am confused on one specific topic - email blacklisting. My confusion is the following:

We are going to be hosting a variety of sites. Each site will have the capability to send out email newsletters from their specified domain-name. I'm looking into a blacklist service, but my question is - since all of the hostnames come from my server IP, why would I check the sites hostname instead of just my IP? Does this make sense at all? So, in summation, my question is - do blacklist services check my IP address, or the hostname that its being sent from? How specifically do blacklists work? Also, are there any free services available?


closed as off topic by TFM, haimg, Dave, BBlake, Diogo Jan 17 '13 at 15:24

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I work at a company which offers an email marketing product, and there are a few things we do to help avoid issues.

  1. Both Microsoft and Google provide "whitelist" services for Hotmail and Gmail (respectively). It's a bit of a pain to setup but worth the effort.

  2. We operate mailout servers whose job is soley to send the mail itself - these machines are dispensable and as such easily removed and replaced if a block is encountered.

  3. We send mail in bundles - not all at once. If 10 users decide to email their 10,000 contacts at once, 100,000 emails aren't leaving the server network at once. The mail is first split across the mailout farm, and then sent in groups of (e.g. 1000). This helps prevent encountering blocks as a huge volume of mail isn't hitting a server from one IP address all at once.

You may also want to consider using an established email marketing service and their API to conduct the mailouts to avoid alot of headache.

And as BillThor said, get to know documented standards. Also be aware of any legislation affecting bulk mail in your area. E.g. in Australia we have the Anti-Spam Act 2003


I commend you for asking questions before you setup your servers.

If you get blacklisted, it will most likely be your mail server's IP address which gets blacklisted. You can quickly get blacklisted if one of your clients harvests addresses from the network. Double opt-in verification is the best policy to ensure the addresses are valid. Your client's domains should have little impact on getting your server blacklisted.

There are a variety of blacklists which use a variety of criteria for blacklisting. Many are free for low volume users. The Spamhaus Project is one I find reliable, and their site provides good documentation on how their various blacklists work. dnswl.org provide a whitelist.

It has been my experience that mailing list operators tend to configure their mail servers very poorly. My rant on Running an Email Server began from my frustration with the quality of mail server configuration. You may want to start with it as I outline a number of steps for configuring a mail server.

Get to know the RFCs for mail servers, SPF, and DKIM. These outline a lot of the key concepts you should consider. If you don't get these configured right, you will have delivery problems even if you aren't blacklisted.

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