AntiSpam: A personal mission
Sender Protected From is a minimal requirement these days. Google will have problems with business email that does not pass SPF. If it were only used perfectly, it would be very difficult for spammers. My online version of the SPF record check tool
Domain Name System MX record verification tests the MX records of a domain for the ability to recieve mail. If a domain is not configured correctly they must not care about getting email.
AI can now read spam and tell you - so you don't have to. See spam-filter.
SPAM is more than a nuissance. I have a service-solution. I will customize email for you.
I provide a special program dedicated to solving this problem at prices set low to near cost. Contact me for details.