This is the reason you shouldn't select "This will be Spam" unless it is spam - clicking that may cause other folks to end getting hired too as it affects the transmitter's reputation overall.
Sender can indicate:
The e-mail address within the "From: " field of a contact. (Unreliable, as it may be spoofed, and frequently is through spammers. )
The internet protocol address associated with computer giving the e-mail. (Unreliable, since botnets regularly deliver from thousands and thousands of compromised PCs owned by normal customers. )
And even though notably unreliable, the trustworthiness of a transmitter is actually a determining that is significant in server-side spam detection.
Tools Run Amok
Another scenario that we hear constantly are PC spam filtering tools gone crazy, typically as an element of a protection suite an instrument is installed that integrates together with your email that is PC-based system. That device scans your e-mail you see it and adds spam filtering or augments the spam filtering already in the program for you before.