Okay, using the hint by "thecloud" here is a simple way of getting OSX to accept self-signed certificates.

1) Get the .pem file. For my imap server running on Red Hat Linux it was in

/usr/share/ssl/certs

and the file was imapd.pem.

2) convert it to a "crt" file:

openssl x509 -in imapd.pem -out imapd.crt

(you should be able to do this on either the Mac or the remote server).

3) Copy the imapd.crt file to your local machine.

4) In Finder, double-click on it, which should bring up the "Keychain Access" app.

5) A dialog should appear asking if you want to add the certificate to your keychain. Now this is important: you have to choose the "X509 Anchors" keychain in order for this to work. It did not work just on my keychain. You will need admin access to do this, and the dialog will prompt you for your password.

That's it. Worked for me.

thanks.

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