Email certificates - what's the deal?

[Simon]

Just this last week, I thought I'd try a different security suite on my Windows 8.1 laptop, so removed F-Secure, and installed Bitdefender.  It worked fine, for the most part, but every time I launched my email client, it kept asking to confirm the certificates for all of my IDNet email accounts.

When I investigated, it seemed that Bitdefender had installed it's own certificates, which appeared above IDNet's GoDaddy certificates.  I poked about in Bitdefender's settings, and also those of my email client, but couldn't really find anything related, so, to cut a long story short, I removed the trial version of Bitdefender, and went back to F-Secure.

Once F-Secure was installed again, I launched the email client, and there was no certificate warnings this time, so I thought all was good, but when I went back into the Certificate Manager, it was still showing as the Bitdefender certificate being there.  Highlighting it produced an option to Delete, so I deleted it, and the GoDaddy certificate, thinking it would be best to start again with a clean slate - but now I have no certificates at all!   

I had assumed that by running a mail check, or restarting the mail client, this would trigger some sort of certificate reinstallation, but it hasn't. 

So, do I need this certificate?  I can still send and receive emails, connecting with SSL/TLS, so as far as I can tell, everything seems to still be working normally.  If I do need this certificate, how do I get one?