I can only second the suggestion that you consider using multiple e-mail addresses. If you have a TA (or TAs), make sure that your students know to use an account that the TA(s) are responsible for clearing for you.

For each of your other e-mail accounts, have a rule that either auto responds with a well worded "if I am able to respond to your request, I will do so in XX days/hours" or scans for messages from people you want to repond to more quickly. In this latter case, the rule would either forward the messsage to a more frequently checked account of would tag it so it gets your attention.

Take every opportunity to calibrate the expectations of others to match what you can comfortably accomplish. In making this calculation, you may want to consider when you realistically can work with any of your e-mail accounts; and take asymetries in available time during the work week into account. For example, you may want to tell students (of the kind where you really must reply to e-mail) that you work on e-mail on certain days and not on others (or particular set times . . . again . . . depending on your situation).

There was a time when profs would post their available office hours for each of their classes. Students knew that individual (or even group) access outside those hours was just not something that they could reasonably expect. If this sounds appealing to you, you may want to consider setting up your own forum or chat channel, moderate their use along a more tradition model, and use either instead of e-mail.