I found this site. But if I use it, doesn't it mean that port25.com would know and be able to use my private key?
You can use that to generate a sample configuration, but should use openssl to generate your real keys.
\\ Generate a private key openssl genrsa -out domainname.com.key 1024 \\ Generate a public key openssl rsa -in domainname.com.key -out rsa.public -pubout -outform PEM
After running those you'll have two files:
# lc total 3 -rw-r--r-- 1 chris chris 887B Jun 5 15:51 domainname.com.key -rw-r--r-- 1 chris chris 272B Jun 5 15:51 rsa.public
With contents like:
# cat * -----BEGIN RSA PRIVATE KEY----- MIICWwIBAAKBgQC7aa4feMEPMy5NXPvaMAPvboFkQqRqCVTMnMeSr4L4oqvd7nou 06nozt6nLtQZnA/KBLDy0ypq2ewTv5te+He5UIDW+VWoaHgZV1FXtfl5f12Ne4bO FVk8XwaIKBJQgtA5iJKoBGxg4A2VoCwxUdW9+LukTtAlFANPdvyCnMsVDQIDAQAB AoGACGnAFU2YbRRBGdv4uly5cIAnctbDBreQhPbsxpr2aC71RCs2dO+vivHucNbb UqL82nbHcr8kAlPyExjg4qyIw0c8JC8AgPKQulmH8K5F1sIFuaJT/3ey/syjT7MS uKmoCtT5XoagTCOiOpclhCA9ixtFjg4+dlkQiLgEXQq8rgkCQQDgC3v8fh3lbiXB fkuE1IaP1mJRwnb1QfZdAa3zM+rk2gG15C1/VYTb4tzscddHcU2/yJ3XOjCBXkMp 2LMVkQ43AkEA1iSnz1woQ+TNn7gN6euaXaXT+Aap/ZeqSCTYQjuG0vrf2Ub5Nw04 m143GmWpa4fS08eTczCeHtZRWAJ6gVV02wJAaScatyPeFjt/PvRur1YsHcBJ/wOd X3jpDzflk5rPaT+kw+DnNbdGlwlAFT1NA/v6uMOIyWZHM8CxFyfczYd6OwJAW0cu nG284AvENiN/EsmRd/96VcuJZAXk2HGUGM9EzeOPzQ66peOl0Fwdgsv4plQz4n+8 cyozDBPwgmI0E7L4ZwJAWFloVLmfMK7S6JF3ADN5Pze9R64Uv84Y5nIpWbyDU6RQ +T7EHSqk7+ajlNetb/6atX4SXK0AK39QjOiOpF9MSw== -----END RSA PRIVATE KEY----- -----BEGIN PUBLIC KEY----- MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC7aa4feMEPMy5NXPvaMAPvboFk QqRqCVTMnMeSr4L4oqvd7nou06nozt6nLtQZnA/KBLDy0ypq2ewTv5te+He5UIDW +VWoaHgZV1FXtfl5f12Ne4bOFVk8XwaIKBJQgtA5iJKoBGxg4A2VoCwxUdW9+Luk TtAlFANPdvyCnMsVDQIDAQAB -----END PUBLIC KEY-----
Yes, if you use their wizard and add the DKIM record it provides they will have all they need to send validly signed mail from your domain.
In general, something strange is going on if someone else is providing you with what is supposedly your private key.
From my point of view, port25.com having that wizard makes them look unprofessional, possibly even suspicious. Even if you trust them (maybe you have a business relationship with them?), they deliver the keys to you in the plain over the Internet.
port25.com is asking you to provide a
DomainKey Selector (e.g., key1) - which is NOT the same as private key that you generated using
openssl or some other tools.
To make it easier, try use more native tools instead: DKIM Core Tools
- Generate a DKIM Core Key
- Check a published DKIM Core Key
- Check a DKIM Core Key Record
DKIM Core Technical Specification covers following:
1. Create the selector and associated key pair 2. Publish the public key 3. Attach the token to the email 3.1 Find the body hash 3.2 Find the header hash 3.2 Generate the DKIM-Signature header 3.3 Multiple Tokens