Reply Allcoholism is a mental disorder that makes it difficult to refrain oneself from hitting Reply-all in an email thread causing pain and suffering to others receiving the emails.
Reply Allcoholics tend to share useless commentary that does not pertain to everyone on an email list which causes them to be hated by most of their friends and family.
There are no cures for Reply Allcoholism, but there are preventative measures one could take.
Jack: Sam is so annoying! Why can't he stop hitting reply all on our group emails and only email to the person that he's responding to?!
Jill: Don't be insensitive, he suffers from Reply Allcoholism.