Set your other accounts to forward them to your gmail with ARC headers, which gmail now supports. Used to be forwarding into gmail was almost unusable due to spam false positives, but I've found it to be significantly improved now (albeit not perfect).
I switched to doing this just last week (having been using POP3 previously). It's honestly a lot nicer in IMO, since the emails show up on the gmail side pretty much immediately instead of sometimes being delayed.
Unrelated, but I noticed this in your two comments and it seems to be something you do frequently—you’re using the wrong side of the quotation character as the apostrophe. You’re using ‘ but it should be ’. See the difference: I‘ll VS I’ll.
Hmm, I transitioned from Gmail to my own domain years ago, but it's still Gmail. However, I'm still both receiving and sending mail from my old @gmail.com address, using POP. Do you know if that's still possible?
I also have an old Gmail account that I don't use directly anymore. Instead of POP, I set it up to forward everything to my mailbox.org account. It works for me this way for several years now. The only issue is that I don't get the spam forwarded, so you can't see if there are false positives. You can still see it in Gmail if you occasionally log in. For me, since this is a rarely used account, the spam I get is usually indeed spam, so I don't miss it. It might be different for a more active account, though.
