Not knowing how you're reading your e-mail messages, it's hard to be any more specific than this: Virtually all webmail and e-mail clients have a "mark not spam" button/function for things that land in spam in appropriately. Once you use that function a couple of times, that tends to fix it.
I don't know exactly what you mean by "my server migrated me emails to Google Mail," in this context. But you can definitely also set up a Gmail filter that says if something comes from the groups.io domain it should not be marked as spam. That probably won't be necessary, though, if you unmark as spam for a day or two.
Brian - Windows 10 Pro, 64-Bit, Version 2004, Build 19041
The purpose of education is not to validate ignorance but to overcome it.