Below is my response (slightly amended).
The reasons for your Mailchimp campaign open and click rates dropping for Gmail and Hotmail are likely:
- Gmail has significantly increased the effectiveness of its promotions tab this year. I’ve had quite a few clients who have noticed a difference in open/click rates from Gmail due to this. See
- Inbox by Gmail is getting more popular and has the same effect as item 1 above.
- Microsoft Outlook (Hotmail) app: In January this year, Microsoft split messages into two sections in its Outlook app; ‘Focused’ and ‘Other’. It is possible that many of your messages sent to Hotmail aren’t being seen by recipients because the Mailchimp messages are going to the ‘Other’ tab.
- I work with many clients identifying which email addresses Mailchimp will and won’t accept and I have certainly noticed that the ‘value’ of a subscriber with a free email address such as Gmail, Hotmail or Yahoo has lowered (i.e. not good).