DKIM - bad signature

[sehh]

Hello everyone,

I'm having problems with our cPanel/WHM server and DKIM with outgoing emails. Every time the server sends an email (via a PHP script), the receiving server rejects the email because it fails to verify DKIM.

For example, here is what a remote server with postfix/opendkim reports:
opendkim: bad signature data

I tried an online DKIM test tool (dkimvalidator.com) and that also reports something similar:
result = fail
Details: message has been altered

I'm at a loss as to what causes this. My PHP script sends a pretty basic email with minimal headers (From, To, Reply-To, Date, Message-ID, etc). I can see that all the proper DKIM header lines are added by cPanel's exim and I can also verify that cPanel's dns properly resolves the public key (default._domainkey.).

I've created 3 domain accounts in this server, all 3 of them exhibit this problem with outgoing emails

Any help would be appreciated.

PS:
Running cPanel/WHM stable channel (11.54.0.24).

PSPS:
I forgot to mention that the same script is working fine on another cPanel/WHM server and the emails sent from that one validate DKIM fine.

 

[cPanelMichael]

Hello,

Is this only happening when sending email via the PHP script, or can you reproduce the issue when sending email from an email client? Is the PHP script using SMTP authentication to send the message?

Thank you.