Someone has been sending blank emails on my email and when I check the sent folder there werent any emails. Does anyone know how this happens?

Just to clarify, is your account the one being used to send out blank e-mails? If it is, how did you know that it has been used since there are no signs in your Sent folder?

If one of your contacts received a blank e-mail from you, can you ask him/her to send you a copy of it with its full headers exposed? If you can and once received, post those information here for us to check it out.