Are you saying that you are seeing messages in your sent folder that you didn't send? If this is the case I strongly advise you to change your passwords immediately, not only for your email but any other online service you use. Seeing messages in your sent folder that you did not send is usually a good indication that your account security has been compromised and someone is now able to send emails using your account. This is a common practice by spammers and once they have your account credentials they can perform something called email spoofing, which allows them to use your email account but attach any "From" name that they like to the emails being sent out. Generally they are not even logging into your email platform to send the emails but using email programs to mass send the emails using your account information.
I had a client that had just over 20 email accounts on their domain for employees, and more than half of them had been compromised and were being used to send spam email from. When we investigated the situation we found that these accounts had very weak passwords, making it easier for the spammers to hack the password and gain unauthorized access to the accounts.