создаю txt запись для основного домена
селектор mail
со значением
"mail._domainkey IN TXT v=DKIM1; k=rsa; p=ключ"
сервис
dkimcore.org/c/keycheck This is not a good DKIM key record.
зы. таким же способом добавил spf - получилось
выдержка из фака
"Type: TXT - Lets you create TXT records, used for a number of different things, most commonly for DKIM records (for combatting spam) so other receiving mail servers can verify email was sent from you by verifying your publically published crypto-signature. Wrap your TXT "destination" in quotes (don't worry, the system will remind you if you forget)."
