If the email is originating from outside your country area, you can/maybe block entire country IP addresses which will stop anything from there coming through to you. It depends on what's available to you from your ISP provider. If you have a server account and your mail is connected to that domain name, you possibly have the IP blocking available to you. Just imagine how much spam gets blocked if you cut out Russia, Nigeria, and China. Since you use this for business you are a bit limited in how much blocking you can do. If it was a private home email account then you could set positive filters which means ONLY the email addresses you'd approved could come through to you and all others would be blocked, but even that wouldn't stop emails using your own email address. If you aren't using your own domain name on a server with mail service, or can't block IP address ranges, then your choices are mostly limited to what blocking you can do at your ISP webmail interface and then what you can do with your own email client software used for IMAP or POP3 mail service. Blocking at the ISP webmail by marking such emails as SPAM or JUNK will add to that ISP's process of stopping spam and might be effective since your ISP likely will also use IP blocking software for their email server. Your contribution of such spam alert helps them identify and block it by IP address too.