Link: https://support.google.com/mail/answer/16604719?hl=en

First, Yahoo cancels simple mail forwarding. Then I try to use the Google gmailify feature to get my email as well as be able to send mail on behalf of my domain name. Next, Google cancels gmailify so now I have recently switched everything over to Fastmail, which offers both of these features plus the label organization and filtering capabilities — but for a price of course. Anyway, I’ve been using Gmail for many many years since it was Beta as my default mail client but now that time has come to an end sadly…

😦