This will let you make simple item lists to automatically mail to specific characters when opening a mailbox. You can set it to require holding shift to send things. There's also a simple system to send uncommon or better BoE equipment to a specific character.
To open the settings window, use the command: /automail
To only mail an item if you have a specific amount or more, you can put +<amount> before the name, like: +20 netherweave cloth
This addon was originally made for the old 2.4.3 TBC client and was converted a few days before the release of TBC Classic. From the testing I could do as a guildless, tattered feral without many resources, it seems to be working.