Thunderbird emails can not execute scripts (javascript, vbscript etc) nor are remote images allowed. So the process of opening an email is not very risky. That is not to say there is no risk, but the same can be said about taking our next breath. /there is risk, but we all do it anyway. Clicking links and opening attachment however do have an element of risk that is significantly higher. If your anti virus does it's job and can recognize the embedded risks before you get clobbered then those things are not all that risky. But they rarely are 100% on new threats With links it is always a good idea to look at the status line. So if the link in the mail says it is your bank and the status line is to a web site say "HonestJognsBoats.com" you know you probably do not want to go there. With attachments that are not expected or unknown senders, save them to your desktop, scan them with a scanner or preferably two before you attempt to open them. One of the sad things about current risks is that they are more likely to come from a trusted source than an unknown mailer. An email from a mother, son or cousin is more likely to be trusted, so the folk sending out many of these new style threats research your mailing habits and send you an email purporting to be from a regular correspondent. Things to watch for. Holiday snaps from someone who is not on holiday. A letter of demand from a business you normally do business with and do not owe money to, a note from your bank asking you to log in and check your account (they have detected some funny withdrawals). The trend is to trick you into opening attachments in particular but also to click on links by using your desire to protect yourself or keep up with family events against you. The old days of unknown sources being the risk are not as great as they were. these days the email is more likely to be unwanted spam than a threat. But remain vigilant.if it feels wrong, more often than not it is.