Checking the kmail for attachments would be the hard way to do it. Refreshing inventory is a lot easier, and much less of a server load (I think) than it used to be now that api.php can be used. That probably removes most of the argument against this.
This request assumes the user is in chat to get the notification immediately. Otherwise, the notification might show up after inventory has been refreshed for another reason, such as logging in.
"assumes the character is in chat" is probably another reason why it was not done. I have an illiterate character to thwart such assumptions
I'm beginning to recall suggestion/discussion that this not be implemented because there were no "push" notifications of mail arrival without chat.
I'm reluctant to require chat on general principles, but it is true adding some kind of inventory refresh would not change my experience.
It is a source of mild frustration that faxes do not respond success or failure correctly unless a chat window is open when they are requested. Perhaps this request would spur development of the ability for KoLmafia to silently open a chat channel (i.e. no GUI) so notifications can be responded to.
I stopped having chat windows open by default and/or at startup. I had some system instability - specifically mafia would appear to freeze and not display the main GUI - and my much atrophied debugging skills suggested a threading issue involving the chat thread. The problem was frequent but not reliably repeatable and it has not reoccurred since I stopped opening chat at startup.
If someone wanted this badly enough and it was not baked into KoLmafia, would a chatbot be a workaround?
I'm just thinking out loud. I'm not necessarily opposed but I am not motivated to implement it myself, either.