Trouble sending public keys from one email client to another?

Trouble sending certificates (public key) from one email client to another? This issue may not be caused by the certificate (public key) itself. Thanks to forum ID 'Griff' for this information. Below is one possibility: In this case Thunderbird was the receiving client. The receiving email client would not recognize that the incoming email had a digital signature attached, and therefore couldn't/wouldn't add the public key to the Certificate list. The message source indicated that the digital signature was indeed in there, but it did not look quite right. The email server in question used DSPAM for spam control, which inserts a Token into the email body showing its Dspam Verification# in the email. The insertion of the DSPAM Token corrupts the Digital Signature information, which is why the receiving email client couldn't/wouldn't interpret it properly. Reconfigured DSPAM (this is a server-side config only) to insert the DSPAM Token into the HEADER only rather than the email BODY. Related Item: Click for Forum Topic on Digital Signatures, Certificates, and DSPAM