If your email address is easy to find online (on the web), then you may become a victim of backscatter.
Spammers use automated processes (programs) to scrape valid emails from the web, and use them to try and lend more validity to their spam emails. It's not practical to prevent, however, you can reduce the occurrence by:
- not publishing your email address on the web (such as by using a form to contact you instead), or
- trying to obfuscate your email address, presenting it as, for instance, yourname (at) yourdomain.com, instead of yourname@yourdomain.com.
If you are a victim of backscatter, then you can expect to receive more such emails, until whoever the sender is (some spammer) starts using a different sender (usually not more than a few days).
Understand that your business may require you to publish your email address, so some or all of this advance may be impractical. In such case, this is one of the less-than-desirable vulnerabilities of our current email system as a whole, at least for now, we must live with it.
More info on why it's wise to minimize the public use of your email: https://www.nytimes.com/2023/01/25/technology/personaltech/email-address-digital-tracking.html
