Rate control for bulk email
June 3, 2008 8:15 AM   Subscribe

When sending bulk email, how much do you need to throttle the rate of outgoing emails to avoid ending up on spam blacklists?

I'm writing some code that sends out email bulletins to a few thousand subscribers. (These are people who have voluntarily subscribed to our mailing list.)

It's easy enough to pause (for example) one second between emails, but some of these bulletins contain breaking news, so I'd like them to get out as quickly as possible.

What's a safe lower limit here? Someone suggested 750ms, but I'd like some other opinions.
posted by greenie2600 to Computers & Internet (3 answers total) 2 users marked this as a favorite
 
Disclosure: I actually work in this industry.

You're probably not going to like the answer, but the truth is that each ISP and corporate spam filter (if you're sending B2B) is different. You're not going to get a silver-bullet answer to this one.

Truthfully, this isn't even your biggest concern, especially if you're sending B2C - you're going to want to make sure that your setup is entirely in line with the various authentication systems your messages might run across (SPF/SID, Domain Keys, etc.). If you all of a sudden start sending emails from a quiet IP address in the thousands, you're probably going to be blacklisted at first, as well.

Your best bet is to start very small, build up a reputation on your IP address (a good one, that is), and respond quickly to blacklist threats - make sure you are sending to a list of folks who have subscribed specifically to YOU. If you're doing co-reg or buying lists, just stop, because you're a spammer.
posted by po822000 at 8:29 AM on June 3, 2008


After posting, I re-read your question, and it's good that they've opted into your list. That'll make it much easier to deal with blacklists and corporate gate-keepers if you're operating in this manner; especially if you keep a record of when and how each subscriber was added to your list.
posted by po822000 at 8:33 AM on June 3, 2008


Cool - thanks for your help!
posted by greenie2600 at 1:31 PM on June 4, 2008


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