Spam coming from wordpress@yoursite, no more contact form

Hi

I am receiving spam emails coming from wordpress@mysite and [email protected], their heading looking like they are coming from a Contact form.

I checked the above email addresses and it looks like they are indeed coming from my sites, but I had deleted Fast Secure Contact Form plugin maybe one year ago, leaving just a contact page with address and email-to.

I had a look in wp-content/plugins with the file manager to see if there was any old contact form plugin folder left behind, but I did not find any.

I double checked both sites with Wordfence Free, that is installed on both, and with Sucuri online, and there is no sign of malware.

What could I do next?

Thanks!