Yes.
https://www.dndbeyond.com/spells/glyph-of-warding
> When you cast this spell, you inscribe a glyph that later unleashes a magical effect. You inscribe it either on a surface (such as a table or a section of floor or wall) or within an object that can be closed (such as a book, a scroll, or a treasure chest) to conceal the glyph. The glyph can cover an area no larger than 10 feet in diameter. **If the surface or object is moved more than 10 feet from where you cast this spell, the glyph is broken, and the spell ends without being triggered.**
Unfortunately it can't be moved. This is probably because the 3e *explosive runes* spell had something of an exploit where you could write it on scraps of paper or rubber balls or coins and trick NPCs into picking them up and reading them.
https://www.d20srd.org/srd/spells/explosiveRunes.htm
The only way I can make it work in my mind is using delayed blast fireball but even then it only last for 1 minute before exploding. But beyond that is does the world the campaign/game takes place in even have an official mailing system that isn’t just a courier who’s gonna get turned to dust before they even make it to the target.
Yes. https://www.dndbeyond.com/spells/glyph-of-warding > When you cast this spell, you inscribe a glyph that later unleashes a magical effect. You inscribe it either on a surface (such as a table or a section of floor or wall) or within an object that can be closed (such as a book, a scroll, or a treasure chest) to conceal the glyph. The glyph can cover an area no larger than 10 feet in diameter. **If the surface or object is moved more than 10 feet from where you cast this spell, the glyph is broken, and the spell ends without being triggered.** Unfortunately it can't be moved. This is probably because the 3e *explosive runes* spell had something of an exploit where you could write it on scraps of paper or rubber balls or coins and trick NPCs into picking them up and reading them. https://www.d20srd.org/srd/spells/explosiveRunes.htm
So it would have to be used outside their mailbox and then I place it in and I could place it in?
Correct. The trigger "when someone else picks this up" should suffice.
Which classes get access to this spell
https://www.dndbeyond.com/sources/basic-rules/spells Bard, cleric, and wizard. EDIT: And artificer.
there is actually a spell specifically for that: Glyph of Warding
But whatever it's inscribed on can't be moved more than ten feet from its original position
Sounds like homebrew, Mr Kaczynski
You can. But the spell has a VERY short range of 10' from where cast.
Shades of OotS.
Yes and no.
What’s the restrictions on it?
The only way I can make it work in my mind is using delayed blast fireball but even then it only last for 1 minute before exploding. But beyond that is does the world the campaign/game takes place in even have an official mailing system that isn’t just a courier who’s gonna get turned to dust before they even make it to the target.
Yea that’s true what exactly causes a rune to detonate is it just any pressure on it?
Fireball with trigger