Usually just a trick by spammers to hide their own email address.
But if you are worried run a full scan with your antivirus program amd install update and run the following free Anti-malware programs:
Superantispyware click here
Malwarebytes antimalware removal tool click here
Spybot S&D click here
A squared anti malware click here
And as a backup scan try one an online scan with many reputable companies – be careful to choose companies that are trustworthy not just those that come up in google sponsored links!!
Eset online scan click here
Kaspersky click here
or download AV scanner Dr.Web ® CureIt! ® click here
if everything id clear after thid lot then you are pretty safe providing you use a decent firewall and good antivirus!
Ask here for more advice if you need it