I use an almost unknown product (like Pegasus/Opera) for my email/web browsing – am I safe?
No. It is true that you’re part of a larger audience if you use the more popular applications – which make many virus authors want to target those applications specifically, but there are innumerable viruses out there that are sent to people specifically because of their choice of applications. And just because the application itself doesn’t have some major design flaw/exploit does not mean that the one behind the keyboard is any more capable of not opening the infected attachment.
An application is not “immune” just because it isn’t “targeted”. The good thing about using a popular application is that you can expect a reasonable response time to complaints and exploits – if a virus does exploit a flaw in something like Outlook you can expect MS to fix the flaw if a patch isn’t already available, which is often the case.
Also, *everyone* you send email to can figure out what app you’re using and someday there will be viruses that exploit this information to tailor the “virus experience” to the flaws within your email application. I’m not trying to be a doomsday prophet, but after seeing SirCam I can see it coming. And it won’t be far off.