It is also dangerous considering that some emails may include security threats.
If you are rocking a linux VPS or a dedicated server with cPanel / WHM installed on it there is a quick way to block most of the email spam in 2 clicks.
It will be 100% accurate for the spammers spoofing email addresses.
The tip consists in blocking all incoming mails which doesn't have the SPF (Sender Policy Framework) configured on their mailing server, which is a simple verification step
You can find the steps below:
1) Login to WHM : https://yourserverIP:2087
2) Click in the WHM side bar on Exim Configuration Manager