Today I wanted to share a small and handy tip to test any DKIM setup.
I used to generate my DKIM key(s) and my problem were that I do not control the DNS’s server which hold my public DKIM’s key pair.
As such at first when I was sending a email to a source like hotmail.com, the header was showing me that;
dkim=fail (invalid public key)
As such, now I had to dig the why, and many website offer to check the DKIM, but I was stumbled on how to do it by hand myself.
I found that nslookup was the saviour.. again.. 🙂
So the tip is to issue;
# There you type your DKIM selector for your domain;
So if your selector is DKIM_test and your domain is contoso.com;
The string will look like that;
The result would be the current key stored for the domain for that selector;
In my case the encryption key was cuted, as some DNS server limit the TXT field to 255 characters, so the field must be split to work good.