Here are the steps you need to take to correct this issue.
Whether your PC is infected with a virus or malware, from another PC, log into your control panel for your email and update the password on your account ASAP. (If you don't take immediate action, this could cause the mail server to get black listed which will then affect everyone else on the shared mail server you're on.)
Then run a thorough virus and malware scan on your PC.
There are many great software out there like Avast and Super Anti-Spyware to scan your PC to make sure that your PC is clean.
Once you've confirmed that your PC is clean, you can update the password on your mail program (Outlook, Thunderbird...etc.).
If your account was compromised by a weak password, then log into your email admin interface and change the password to a stronger password. If you can't figure out a strong password, you can use this website Strong Password Generator to generate a new password for you, then reset your email password in your mail program with the new password.
Here are the links to each of the Customer Control Panels.
FPToday Email Admin Console
SuperAccount Customer Control Panel
HSPC Customer Control Panel
POA Customer Control Panel
If you don't know know what control panel, click here to send and email to InfoQuest Support and we'll reply back with which Control Panel you need to log into.