it allows tracking the source of scam/spam messages.
1) If IP address is going to be used for spam filtering, then the server should be able to do it without revealing the IP to the receiver, just like the web version of gmail(although I do understand that such a thing is not possible when using Aqua Mail or any other 3rd party email client), not that spam is that big of a problem as it used to be.
2) Pretty sure modern spammers would use something like Tor to hide their originating location, so revealing IP address would become pointless in catching them. In the end, it's just less tech savvy users like me who unknowingly send our location to strangers on the internet.
3) If it's a scam, then a normal citizen can only report such an incident to authorities & then the authorities can use their special ways to find the source. What is a normal user like me going to do with the location of a scammer? Confront him & try to solve the problem personally? As if that won't have any repercussions. Again making IP revelation pointless.
Times have changed, but email tech has remained the same
There is a reason why modern services like whatsapp don't reveal the IP address to the receiver, because doing so is a breach of privacy.
