I am in a situation where I use another email provider (protonmail.com) but cannot get rid of Gmail. Too many friends, family, and recruiters use my Gmail for me to actually delete it. I could use two email clients, but having one source for all my emails is just better. These are the tips I suggest for this situation.

Add a “special” Forwarding Address: Forward all new emails from Gmail to your new email address. For example, let’s say your new email is user@domain.com. I suggest putting a +gmail after user (user+gmail@domain.com). Your new email client can label and filter this specific email address now, letting you gradually update services with your new email address. Bonus suggestion is to select “delete Gmail’s copy” so you are not duplicating emails.

Settings > All Settings > Forwarding and POP/IMAP > Forwarding:

Turn off Gmail’s SPAM filter: All emails should be forwarded to your new email provider, but Gmail will not forward SPAM emails. Having double SPAM protection increases false positives. I recommend turning off Gmail’s SPAM filter so everything will get forwarded. There is no SPAM toggle in Gmail, so you need to make a fancy filter. You select all messages by doing a “does not match” a random GUID (or another log and unlikely text) and picking the action of “Never send it to Spam”.

Settings > All Settings > Filters and Blocked Addresses

Label big emails: Eventually you will want to export your emails to your new email provider. Gmail has a generous amount of email storage, probably more than your other provider. To avoid using up all your storage, filter out big emails so you can manually export them, delete them, or ignore them in IMAP. Creating a filter is straight forward.