We recently analyzed the stats for over 184 million emails sent from MailChimp and put together a report analyzing the engagement of recipients by email provider (yahoo, gmail, hotmail, aol, and comcast).
Gmail users appear to be the most engaged, and there are some interesting hypotheses as to why, suggested in the comments.Integrations
MailChimp recently partnered with Eventbrite, and our services are seamlessly integrated. Build events in
Eventbrite, then design & deliver awesome invitations in MailChimp.
Integrating SurveyGizmo with MailChimp was a no-brainer; easy to use email marketing with easy to use online survey software equals one easy to use, well-rounded marketing campaign.

This integration allows
you can have all your help desk customers and users subscribed to a mailing list so that you can send out proactive support information and/or service related newsletters.

Ever since we posted about our
integration with Salesforce, people have been asking for
Zoho,
Javelin, and other CRM integrations as well. We can only integrate so fast, so it helps when other companies actually take the first step and integrate with us (our
API documentation is pretty thorough).

Here's a
nice video tutorial about how MailChimp and Javelin work together.
SugarCRM + MailChimp group in The JungleThis is a forum for folks who use both MailChimp and SugarCRM to get together and talk about what an integration should look like.