Somewhere in the past days or weeks, Google started either bouncing email without a DKIM signature or is silently filing it as spam. (DKIM: DomainKeys Identified Mail, an anti-spoofing measure.)
If you receive email at a domain you registered, there is a good chance that recipients who use Google Mail are not receiving it. You'll need to ensure that you're getting a DKIM "pass" result that matches your domain name.
For example, I use Fastmail. GMail was indicating "DKIM PASS from messagingengine.com" (that's Fastmail's actual mail service) but was still rejecting my mail. Once I added the DNS records that Fastmail indicating I needed to add in their settings page for my domain, I instead started getting "DKIM PASS from [my actual domain]" and my mail started getting through.
(While DKIM is a reasonable tool and it's fine that Google is using this as part of their spam check, I suspect they're doing this strict version to try to solidify their position by further freezing out other mail providers.)
If you receive email at a domain you registered, there is a good chance that recipients who use Google Mail are not receiving it. You'll need to ensure that you're getting a DKIM "pass" result that matches your domain name.
For example, I use Fastmail. GMail was indicating "DKIM PASS from messagingengine.com" (that's Fastmail's actual mail service) but was still rejecting my mail. Once I added the DNS records that Fastmail indicating I needed to add in their settings page for my domain, I instead started getting "DKIM PASS from [my actual domain]" and my mail started getting through.
(While DKIM is a reasonable tool and it's fine that Google is using this as part of their spam check, I suspect they're doing this strict version to try to solidify their position by further freezing out other mail providers.)