Can Mail get infected with malware?

A few days ago I had a strange episode while trying to send email via the Mail app on my macbook. While typing a message the New Message window went black and unresponsive (couldn't close it or type in it) although the main Mail window underneath was visible. I clicked on an old message in my inbox which opened but it was also black, likewise other messages I opened - the message windows opened but were black. Tried to close mail using Force Quit but this didn't work. Had to shut down laptop using the power button. On re-start Mail was working normally.

A few days after this incident I sent mail from a different mail account and using the gmail.com site (i.e. not using the Mail application). This email was apparently intercepted by a scammer and the information contained used to scam the intended recipient of the email. Although I don't have this second email account set up in Mail, it is linked to my other gmail account, the one I was using when everything went black.

Worried I might have been infected by malware or spyware. I NEVER open unsolicited attachments and the black-out occurred when I was attempting to write an email, not trying to open email.

Am using a Macbook Air running iOS Sierra 10.12.6 and Mail version 10.3 (3273)

Anyone else experience this "black-out" in Mail and/or have any idea what it could mean?

Thanks in advance.