SSL IMAP email certificate error message

This is somewhat "off-piste" but I've been so incredibly frustrated by this issue I thought I'd write to: (1) see if anyone can enlighten me; or, (2) maybe be of help to anyone else suffering the same frustrations. 

Security is a good thing, right?  So, with a vague notion that I should activate SSL on my email accounts, I set about doing so on the incoming and outgoing mail servers I've connected my Outlook account to. I use IMAP for incoming mail.  

The instructions I had said that for the incoming mail server I should use server.myhosting.co.uk (no mention of port number). For the outgoing mail server I should use server.myhosting.co.uk (port 465).

When I opened MS Outlook 2003 I had to respond to three identical Internet Security Warning messages:

"The server you are connected to is using a security certificate that could not be verified.
A certificate chain processed, but terminated in a root certificate which is not trusted by the trust provider.
Do you want to continue using this server? Yes/No"

I asked my email provider about this and the response I got was: "You just need to "trust" the certificate in Outlook and then it shouldn't ask you again. Please refer to your Outlook support documentation on how to do this."

To cut a long story short, I couldn't find "the certificate" anywhere (am I really that dim?). Without knowing where or how the certificate could be located I couldn't "trust" it. I couldn't find anything in the Outlook help that was even remotely helpful.

After some scratching around the web looking for answers to "certificate" problems I found something that suggested that I needed to "obtain the certificate" by visiting the mail server using the designated port and "installing the certificate". 

I typed https://server.myhosting.co.uk:465 as a URL.  I got:

There is a problem with this website's security certificate.

The security certificate presented by this website was not issued by a trusted certificate authority.

Security certificate problems may indicate an attempt to fool you or intercept any data you send to the server.

We recommend that you close this webpage and do not continue to this website.

Click here to close this webpage.

Continue to this website (not recommended).

More information

When I clicked on "Continue to this website" I got a certificate error message in the box beside my URL box.  I clicked on it and clicked on "View certificates" and then clicked Install certificate... | Next | Next | Finish | Yes | OK | OK in sequence.  You need to take your own decision about clicking on Yes in the previous sequence - it's your decision, not mine.

Noting that Outlook set my port number to 993 for the incoming IMAP setting I tried the same approach there using https://server.myhosting.co.uk:993 but got a page not found error. 

What to do? I decided I'd try the incoming mail port used for POP3 protocols (995). So I typed https://server.myhosting.co.uk:995 as the URL.  I thought I was out of luck as it took forever to connect - but then it did.  I "installed the certificate" and re-booted.  It did the trick.
 
I can't believe that coming to something that appears to work has been as random as what I've done.  I feel that I just don't "get" how this is supposed to work. I'd love a simple explanation of the theory of SSL email so I could have more confidence that all of this isn't going to come back and bite me again when the certificates expire in a year's time.

I'd love to hear some other experiences on this.