Setting up your DKIM is a simple two-step process. Let's say you are using "example.com" as a domain.
1) Start by adding a CNAME record with the following Name and Value:
Address, Name or Host: critsend2._domainkey.example.com
Value: dkim.critsend.com
Note that sometimes your domain name might be automatically added to this field. In such cases you will have to leave off "example.com" in the address field.
If your DNS client doesn't support CNAME's with underscores, you will need to add a TXT record instead:
Address, Name or Host: critsend2._domainkey.example.com
Value: k=rsa\; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCvEpIr9ILg7iXsdMlMst5sCK+MDc4GQDaZDmgLLHHVNn952Jh4zmB1Qp+fBSUzVfcU/qW4hicOMJKRe0bo8nIB/Gvh3CtJuyAFizXCUjDtn2V4t5rg2OEpVkEXHkwUoW43Z5753Q62flW2wb3zuEqoO5fWLUt4rcIqatE+O8zmSwIDAQAB
2) Log into your Critsend account, go to "Account -> Mail Settings" and find the "Signed-by Domain" line.
The corresponding value will be used by email providers to check for an appropriate DKIM record. For instance, if you've used "example.com" in step 1, then you would need to enter "example.com" in this field.
Warning: Hotmail's DKIM verifying procedure needs the "From" address domain to be the same as the DKIM signing domain. So, if your signing domain is "example.com", your "From" address should be something like "hello@example.com".
That's it. If you haven't set up your SPF yet, we recommend that you do it immediately. Read more about how to do it here.
3) Test your settings
Once you've set up your DKIM, you can test it here. Use "critsend2" as Selector and your own domain name as Domain Name (Wait 4 hours for DNS propagation though.)