The contrib is just here to give your life easier, you have to use a certificate that supports multiple domains if you really don't want to see warnings. However you can also customise your certificate (of course it is valid for one domain)
for example(i don't have a static IP)
my main sme domain is de-labrusse.xx
my dynamic dns is stephdl.xxxx.xx
the sme certificate is of course hostname.de-labrusse.xx
I use the dynamic domain for reaching my server on the internet, and of course you will have warnings
if you use stephdl.xxxx.xx, you will have warning that the certificate is hostname.de-labrusse.xx and it doesn't match
but if you set a different common name which match the dynamic dns name, no more warnings if you use the common name for reaching your server.
http://wiki.contribs.org/Certificate#How_to_change_your_certificatewhen I speak about no more warnings, of course as it is a self signed certificate, you have a non trusted warning.