Security Check Failed

I used the contact form for the following Toastmasters chapter: Club Number: 00001484, 53, Area C35 and received an automated email with the following message: 

WARNING: An email security check failed during email processing. Your email was still delivered.

        (DKIM Signature Verification: fail (message has been altered)

I'm a former Toastmasters member, currently living in Singapore, which I suspect may be why the security warning was triggered. Can you assist me with this? Although the message says my email was still delivered, I'm concerned.

 

I can see that your contact form submission has been forwarded to 3 of the club members