The Mozilla Thunderbird FAQ says the following.
Is Thunderbird susceptible to e-mail viruses?
Thunderbird will not allow a virus or worm to execute automatically. You can see what attachments have been sent to you without a virus being able to execute, and you would have to save a file to your system and deliberately run it before it could cause any harm.
JavaScript is switched off by default for mail and news, so an e-mail cannot run script code just by being opened.
As with any mail program, take proper caution before running any file that you receive in e-mail. Appropriate anti-virus software should also help keep you safer.http://texturizer.net/thunderbird/faq.html#q2.1Can anyone confirm that you cannot run an executable email attachment from Thunderbird like you can from Outlook Express just by double clicking on it? From the Mozilla FAQ above it appears that they are implying that you actually have to save the attachment first before you could run it (e.g. the FAQ says:
you would have to save a file to your system and deliberately run it before it could cause any harm ). Presumably that means that if in a fit of absent mindedness I double clicked on an attachment within Thunderbird it would not try to execute like it would from Outlook Express. Once I saved the attachment to disk even if it was virus infected if my AVG definitions were up to date, the AVG antivirus would catch it when I tried to run it (or when I manually checked it by right clicking on it and scanning with AVG). Am I on the right track here?
I have hesitated switching to Thunderbird from OE up till now because I had concerns as to how Thunderbird would integrate with AVG for anti-virus protection. If my understanding of the FAQ response is correct, and I had to save an attachment before I could execute it, then I guess I would not have a real cause for concern.