on-rev invalid certificate?

[Dom]

Hi!
I am posting here, not knowing there exists an "on-rev" miling list
(if so, tell it to me :-))

So, I took the plunge for on-rev :-)
And, as I am a total noob about managing a web host, I have some
questions!

First: why is Mac Mail.app complaining about an "invalid" certificate
for "mail.medard.on-rev.com)?
[my domain is named "medard"]

I had to specifically authorize this certificate, as it claims that
there is a discordance with the host name!

Dom, not dumm ;-)