Make the mail not crash the game.
What you can do to keep your mail from crashing the game.
Opening de mail box will let you see the last 8 mail that came in.
https://i.imgur.com/nR3eRKr.png
When you now select all en process the mail there is the possibility to click more then once on the green button.
This will 100% crash the game.
If you go to the first mail that came in, scroll down to get there,
https://i.imgur.com/H3eC9k6.png
Now process the mail, select all, choose destination.
You can click only once on the green button because the mail is instantly processed.
https://i.imgur.com/ywjnaes.png
The game will now continue without a hitch.