It's normal for open rates to increase or decrease when first sending from a new platform.
We sometimes see the question "Why have my open rates changed since moving over to ConvertKit?"
When you change Email Service Providers, you start to send from a new infrastructure.
Mailbox providers (MBPs), such as Gmail, Microsoft, etc., create a profile for you as a sender. This profile includes a reputation score that MBPs have calculated based on many factors, but mostly the way that Subscribers engage with your messages.
Any time there is a change to your sending, MBPs have to recalculate your sender reputation.
When you start sending from a new Email Service Provider, you start sending with new IP addresses and tracking links. Because of this change, MBPs have to recalculate the sender reputation score they have for you. During this time it's normal to see open rates increase or decrease.
To help mailbox provider send your messages to the inbox, we recommend the following steps:
Send to your most engaged Subscribers for the first week or two before sending to your full list
Make sure not to send to anyone who previously bounced, unsubscribed, or complained about your messages in your previous Email Service Provider
Ask Subscribers to engage with your messages, such as replying or allowlisting your sending address
It may seem tempting to test open rates in multiple Email Service Providers, but we don't recommend this. Not only can it confuse MBPs, but you'll usually have better open rates on the provider you've been sending from longer.