Sending e-mails

Not sure where else to go so I'm asking here in the hope somebody can help me. Basically none of the options along the top of my inbox work, which means I can't send any e-mails from my account. When I'm in my inbox and click them nothing happens, and if I'm on any other page I just get returned to my inbox. I need to send a couple of potentially important e-mails so it's really annoying me that I can't get into compose a new message. I really don't know how to fix it so if anybody knows why this is happening and can offer me a solution I would be most grateful.

Thanks in advance,

Mark