Email header vs email envelop : what are the differencies ?

Some senders have two addresses: one visible, and one hidden. 

If these addresses are different: check the domain name, that’s the part after the @. 

If the domain name looks suspicious or different from that of your usual correspondent, remain vigilant and recover the email only if you were expecting one from the sender. 

The address that’s visible can be misleading because a hacker can usurp the address of one of your contacts – the one that’s hidden is more reliable, thus the one you should check.

The visible address is often more readable and aesthetic. Sometimes a name can be associated with this address. 

The visible address is called the header address, it is the most visible address in email clients. It is the most telling but also the most easily falsifiable. 

The hidden address is sometimes less aesthetic and can be technical, long, or not very readable. 

The hidden address is called the envelope address, it is the true address of the sender, it is less easily forged but sometimes also less recognizable.