Any tips for migrating off of gmail? Have over 40 accounts tied to it

Just curious to see if I'm missing some obvious shortcut to moving off of gmail.

Decided on fastmail after some research, but the task is starting to look daunting. I've counted 40 accounts so far and I imagine there are at least 5-10 more minimum.

Any ideas? Or do I just have to go through the pain of doing each one, one by one?

Lastly, any best recommended practices for letting contacts know? Current plan is to forward emails to fastmail and just start replying with my new email address and overtime have people's contacts update automatically.