Well, here goes. They say that the only stupid question is one you don't ask.

When I log in to XMarks I go straight to "new posts". There I get a list of new posts and at the left side of the list each post has an envelope next to it. Some envelopes are blue, some are yellow and some are red. What do these different coloured envelopes mean? I've tried search (didn't find anything), FAQs and even working it out for myself, to no avail. I'm stumped and it's been intiguing me for a while.

Thanks in advance.