An Email Security Check Failed

I tried to contact the Oak Lawn Toastmasters Club (#00872531) using the Contact Form on their site and I got a return email that my message was not delivered:

An email security check failed during email processing.
(DKIM Signature Verification: fail (message has been altered))
Emails failing security checks may be blocked in the future.

What does this mean?

Saundra Washington
Pathfinders Club #2734

This means that our email security code thinks that the email was altered on its way from you to the FTH server. "Altered" typically means that the email subject or email body was altered in some detectable way, but unfortunately this warning can get triggered sometimes if the email was forwarded quite a bit on the way to us or if it went through a lot of intermediate processing on its way to the FTH server.

It is just a warning. Despite what the warning says, I am not confident enough in the triggering logic to make this an actual error that blocks emails. (I may never be that confident.)

Hi Steve,
Thanks for the reply. Actually, my email did go through and someone from the other club answered it, even though I was led to believe my message had not been delivered. I hate to think that visitors trying to reach our clubs get warnings like this.

Saundra Washington, DTM
Pathfinders Club

This is a very infrequent warning. I am not going to get rid of it, but I will look into improving the wording a bit.