Using dig on my domain returns this:
auth._domainkey.thundercraft.com.br. 1800 IN TXT "v=DKIM1"
Also http://www.brandonchecketts.com report as invalid
DNS: auth._domainkey TXT v=DKIM1;k=rsa;p=MIGfMA0G [ ... ] 8QIDA...
I followed this guide https://library.linode.com/email/postfix/postfix2.9.6-dovecot2.0.19-mysql
DNS are:
Domain1
A mail.domain1.com > vps_ip
Domain2 (emails from here)
MX mail.domain1.com
Domains3 (emails from here ...