Got sent gold as a thank you, can't Take All

I was running organised gold Boss Blitz runs yesterday and a nice player tipped me 1 gold.

I can't get it out of my mail. I can Reply, or Return to sender, but I cannot Take All. (I also can't Delete, but it would be nice to get the tip).

maybe you hited a limit :"An account can only accept up to a total of 500 gold through the in-game mail system and/or the Guild Vault each week. If this limit is exceeded, you will need to wait until the following week to collect any remaining gold."

Likely not a bug, you probably hit the weekly gold limit of 500g from any sources including mail, guild bank, etc. Just wait a while for it to reset and then you'll be able to accept the mail, and in the future use Mystic Coins or similar instead of liquid gold when trading with friends and guildmates so that you don't hit the limit when you get sent random mails from other players.

Ah, thank you, that will explain it.