Email certificate is one way to digitally sign emails and make sure your email stay secure plus makes sure that the email and attachments content actually came from you. Whenever anyone edit the content of your mail, the recipient will be alerted that the email is being compromised. Here’s we will see how to install the email certificate on Mac OS X.
First you have to get your email certificate from the CA (Certificate Authority), i use free email certificate from Comodo CA. FREE ??? Yes it’s absolutely free, and this is ideal for personal use, to get it you just need to sign up here using the email you want to get certificate, if you have multiple email you’ve to sign up multiple times.
Just wait for the certificate being sent to your email, usually it just take several minutes to collect the certificate. After receive the email confirmation, just open the link using Safari for Mac. Yes it needs to be Safari not others browser, it takes several hour for me to figure it out, but that’s how it works on OS X. The Safari will download the certificate and you need to install it to OS X using “Keychain Access”. Just open “Keychain Access” (search for “keychain” using spotlight) and drag and drop the downloaded certificate to login Keychain – My Certificates category and viola the certificate already installed. Restart Mac Mail and soon you will see the option to sign the email beside the Email Subject.
Beside the benefit, there’s another disadvantage on using email certificate which is not all email software handles S/MIME signatures, resulting in an attachment called smime.p7s that may confuse some people. I receive several people asking me what is smime.p7s they receive on their email attachment, which is sometimes annoying me. I just told them to ignore it :).