I don't think there is an easy way to do that. There are mailing services, and sites that support polls that might be able to do it, but I fear it wouldn't be safe (meaning reliable) to do via email. I'm doubtful if a polling site can help, since you need to know ''who'' voted yes or no, not just how many yes's and no's there were. A common way to do this is to offer a link to a website where the respondent can tick the checkbox, but then you have to set up that website, and the accounting mechanism to record the ticks and associate them with the particular correspondent. My experience of checkboxes is that there is code associated with them to accept the click and change the appearance. Users of clients such as Thunderbird wouldn't be allowed to run such code. Maybe just asking your correspondents to reply with a YES or a NO added to the subject line would be a workable compromise. However you ask them to acknowledge your request, you have to do something with the data. Looking a for a ticked or unticked checkbox wouldn't be any easier than checking out the subject line. And you could set up a filter to sort the yes and no replies into separate folders.