Gloryholing through a mailbox slot.
Guy 1: So you get yo dick sucked last night?
Guy 2: Yeah, but i didn't feel like looking at her face so I junk mailed her.
Any sort of unrequested email, text or other social media communication, especially sexually-oriented messages or containing pictures of genitalia on the internet. Abbreviated: DJM
Sending Digital Junk Mail turns your social media into anti-social media especially when it contains pictures of genitalia.