MailChimp are very diligent about spam. If your emails get reported as spam more than %0.5 of the time you'll be banned.

So "Unlimited" has a built in limit.

(We use/love MailChimp, definitely recommended.)

0.1% actually. I kid you not. (This causes me a minor issue once a year. One of my autoresponders caught a flag in January for having 6 / 4000 = 0.15% spam complaints. They were quite clear in their mail: I'm on probation.)

Have I mentioned I love MailChimp? They take deliverability seriously.

(Also, they do have actual human beings who you can talk to if you get flagged unnecessarily. For example, within 24 hours of opening my account and funding it, it was closed because I used the word "bingo" in a draft email. Their filter smacked me down for promoting gambling. I mailed them and the CS department got back with "Thanks for your explanation of what your business actually does. OK, we reinstated you. Be careful.")

I ran into an issue with Constant Contact that basically banned one of my mailing segments of around 500 emails. The rest of the list was okay to send to, just one segment was blocked. The issue was a false positive spam test by Constant Contact and they refused to unlock that segment. Even had they unblocked it, the CS experience was still bad enough to raise a warning flag.

I've since moved on to MailChimp and have been much happier with it than I was CC.

I'm glad to see them improving on an already highly functional free-tier.

They HATE HATE HATE spam. I got flagged one time because I used the word craigslist in a blog post I sent out automatically through an RSS to Email feed. Luckily customer service threw a banana at the spam team and they got me back up and running.

You have to avoid using the word "craigslist" when using mailchimp??

Apparently. Immediately got flagged when it went out. It was a blog post about how I bought & fixed up a bike for $150. I mentioned I got it off of craigslist and it set their filters off.

I work at MailChimp. The answer is nope.

As someone who doesn't know much about MailChimp, the original question seems valid. A little more detailed answer (like the one by qeorge) would have helped me understand this better.

As you work at MailChimp, it would have helped if you would have given that detail.

Ben from MailChimp here. We invested a lot in abuse prevention, well before introducing any freemium plans. The problem ESPs like us face isn't so much the "evil" spam, but the "fuzzy" spam (from clueless marketers).

Our approach to dealing with fuzzy spam is here: http://blog.mailchimp.com/project-omnivore-declassified/

an update was posted here: http://blog.mailchimp.com/update-on-omnivore-new-3-strikes-r...

Probably shoulda brought that up in my blog post (it's usually the first question techies ask), but it's something our customers are pretty familiar with, so I left it out.

Thanks for your answer. I imagined so. But I could also think of some legitimate heavy-duty users who could threaten your profitability. Is there any fine print for those cases?

I don't think so. The cost of running something like Mailchimp isn't in having a couple of servers and some bandwidth, I imagine; the cost is in dealing with spammers, overzealous spam-fighters and people who'd rather hit "report as spam" than unsubscribe. Number of subscribers is not a bad metric.

ETA: Also see bjonathan's comment at http://news.ycombinator.com/item?id=2170619: Amazon, which probably offers something closer to "server and bandwidth", is much cheaper.

No fine-print. Our high volume plans for large email lists are not unlimited, but smaller lists are completely free to send as much as they want. In practice, you'll hit our anti-spam limits long before you hurt our profitability if you try to send lots of email to a smaller list.

Thanks for the explanation. I'm glad you stopped lurking, and to have tripled your karma!