RE: mail program and avast - how to import certificate.
... or simply tell Avast not to scan incoming mails as Opera does not execute anything in mails. Checking the folder where opera stores the mails should suffice.
I personally consider the behavior of those scanners to intercept the connection without showing me the real certificate or allowing me to check from inside of the mail program harmful. I want to be able to check the certs and I want to see immediate warnings and hints because I want to be able to react.
Funny side note:
Some time ago I've got a mail from a person who sent the source code of a web page as text inside of the plain text body, with the warning that it contains some hijacker/trojan code and if I could have a look at it. Indeed it contained some heavy obfuscated evil code. At that time Avast didn't know the hijacker/trojan, but later, when they caught up, it always complained about the stored but in its form harmless mail because it sees the hijacker/trojan code in the text but does not recognize that it is harmless, while it is stored as mbs - at least as long as nobody gets the idea to deliberately make it executable, which I for sure wont