mailgrid.pl has no AAAA records.
Apex domains cannot have CNAME records.
Google
Domain verification
google-site-verification=shErlBW6We0vQbXzk9Mp4T-xkHWjZZWY7cizzTf7wx0
Mail.ru
Domain verification
mailru-verification: 9888ff61ac0b66f9
Yahoo
Domain verification
yahoo-verification-key=4Ttk2yL1zIcKNtr0dS6+7yWL1esOXHNCbp/42YezKn0=
aa2758ddb0f96523b4e0a9168a9ac02820aff8903865392d0e71fc03a41781a
lynn.ns.cloudflare.com
Cloudflare
tani.ns.cloudflare.com
Cloudflare
Zone apex
Start of authority
Email
Serial
2395780210
Refresh
2h 46m 40s
Retry
40m
Expire
7d
Negative cache TTL
30m