Domainkeys identified mail
DomainKeys Identified Mail (DKIM) is a method for signing email messages to help eliminate spam.
The signature in each message should give the domain (d=) and selector
(s=). The appropriate key can be retrived as a TXT DNS record from the host
selector._domainkey.domain
1. A sample message
from Gmail had the following DKIM header:
DKIM-Signature: a=rsa-sha1; c=relaxed/relaxed;
d=gmail.com; s=beta;
We can thus retrieve the Gmail key with:
$ host -t txt beta._domainkey.gmail.com
beta._domainkey.gmail.com descriptive text "t=y\; k=rsa\; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC69TURXN3oNfz+G/m3g5rt4P6nsKmVgU1D6cw2X6BnxKJNlQKm10f8tMx6P6bN7juTR1BeD8ubaGqtzm2rWK4LiMJqhoQcwQziGbK1zp/MkdXZEWMCflLY6oUITrivK7JNOLXtZbdxJG2y/RAHGswKKyVhSP9niRsZF/IBr5p8uQIDAQAB"