How to convert a DKIM private key from pfx format to PEM

You can use the following free openssl tool to convert a DKIM private
key from pfx format to PEM:
http://www.slproweb.com/products/Win32OpenSSL.html
[http://www.slproweb.com/products/Win32OpenSSL.html]

Once you have installed the program and opened it, simply issue the
command below.

openssl pkcs12 -in c:certsyourcert.pfx -out c:certsyourcert.pem
-nodes

Next, open the PEM file in a text editor (such as NotePad or
EditPlus) and ignore all but the last certificate section.

-----BEGIN CERTIFICATE-----

and ends

-----END CERTIFICATE-----

You can then copy and paste everything from the begin tag to the end
tag (including the tags themselves) into the private key text box.