Instead of NoSenderEncryptionCert the code says NoSenderEncriptionCert. This causes the problem, that when something fails during encryption/signing preparation, you don't get a wrong error message. (Instead of reporting failure to find certificates, a general failure with mail news settings is reported to the user).
Updating summary, there was a typo in the word typo...
Comment on attachment 69114 [details] [diff] [review] Suggested fix r=ssaux
Checked in, fixed.
Verified per kaie's comment.