dkim.el generates an invalid signature

[peti]

I set-up dkim.el as per the instructions in the el file, and I get signatures added to my messages, but apparently the signatures don't validate. Citing from http://www.mail-tester.com/web-fzgrjG:

The DKIM signature of your message is:

    v=1;
    a=rsa-sha256;
    c=relaxed/simple;
    d=cryp.to;
    s=dkim;
    t=1459850626;
    bh=dGhkzWmDBVuFEQmbUWeAKcwXdkZ6L34QTgheWcMPMqM=;
    h=From:Subject:Date:To:;
    b=Ng3LBpDDhqVXZgi5OUWfp4aaT2eVEgXDzRLsj6itc0VT523OV+HtU0TFvk5Expx/5H14hfqmH6txQ/ec/+zWNWG0a9wgYYkVfTiAFXEAbJs1nSmnpmN/3Uu/KpKk+qIXspxfZ0sNu1SdZUb/TzaMR1Y8ocpLvV4S4tsxgEEwbzw=

Your public key is:

"v=DKIM1;
k=rsa;
s=email;
p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDcDajLhNGQo2VHwXzk5MMdCFdXEjCwGqMdh8lmUylkyORunoncyeUMVFOvu9Y1ZLu80ycwo/K2tdSZzArEj+9m13lgB8uAdAn0ov3RKv41p1Tw68NILgWsfz2fJGJsE5dIUfnDmmOVYgjZyvwfp2nIYbunBEiMGcIbSn8oB0o6vwIDAQAB"

Key length: 1024bits

Your DKIM signature is not valid

Do you happen to have an idea what might be causing this issue?

[ucko]

According to verifier.port25.com, the only validity concern is that h shouldn't end with a colon after all. Want a formal PR?