Secure socket layer (SSL) is a technology used by some mail servers, which maintains a private connection between the server and your computer. It keeps others from viewing the data transmitted. This is used in banking websites that display the “s” in “https://” in the website address. SSL is now becoming standard and should always be used. Gmail uses SSL, both in POP/SMTP and webmail – as long as the “s” is in the address. There is a Thunderbird extension for Google preferences that adds the “s” automatically.