Hey guys,

About a month ago, we switched email service providers from Constant Contact to MailChimp. It's been a huge improvement from a designing/developing standpoint. But over the course of the month we've noticed a sharp dip in our open rate. Our average has been a consistent 45-49% for the last 12 months. August (so far) is sitting at 37-38%. It's a pretty big difference, especially considering our mailing list is only 2500.

We're trying to narrow down what exactly may be causing our sudden decrease. We haven't changed the frequency of email traffic, the type of emails sent, nor our email list, which is comprised of all our active business dealers (hardly any unsubscribes and delivery rate is 99.75%). We've also gone back through all of our data collected, just to make sure we're comparing apples to apples, and verified the numbers.

Gmail.com and Yahoo.com addresses comprise of the largest chucks of our list at 18.6% and 14.5%, respectively. We noticed that, according to MailChimp's reporting, about 62% of each group are not opening our emails. At first we thought it might be a sorting issue, as tests have shown that our emails are now being delivered to the Promotions folder in Gmail. We were preparing to send a specific Gmail campaign notifying our dealers that due to our ESP switch their emails might be found in a different location than they're used to. However, I'm not aware of any folder system in Yahoo that would push our emails out of the primary inbox and cause the same unopen rate there.

We're also tentatively ruling out design, since the main reason for the switch was to drop CC's unresponsive platform. All of our emails are responsive/mobile friendly and have been testing fine (or as fine as they can in Gmail, HA). Our mobile opens are actually up a little bit from past months.

So what could be going on with our open rate?

Has anyone else noticed drastic differences in reporting after switching mail providers? Should we expect a "warm up" period and, if so, for how long? I understand that a month might not be the longest interval to get an accurate picture, but at the same time we don't want to sit on any potential issues for too long without taking preventable action.