try getting malwarebytes and update it then run full scan.
Malwarebytes' Anti-Malware
download Malwarebytes' Anti-Malware to your desktop.

* Double-click mbam-setup.exe and follow the prompts to install the program.
* At the end, be sure a checkmark is placed next to Update Malwarebytes' Anti-Malware and Launch Malwarebytes' Anti-Malware, then click Finish.
* If an update is found, it will download and install the latest version.
* Once the program has loaded, select Perform full scan, then click Scan.
* When the scan is complete, click OK, then Show Results to view the results.
* Be sure that everything is checked, and click Remove Selected.
* When completed, a log will open in Notepad. Please save it to a convenient location. The log can also be found here: C:\Documents and Settings\Username\Application Data\Malwarebytes\Malwarebytes' Anti-Malware\Logs\log-date.txt
* Please post the contents of that file in your next reply

be sure you allow it to clean what it finds, you may need to reboot.

Go in to your sent folder and right click on the suspicious email and choose Scan with anitvirus. You can do each email this way until you find the two that are infected.