Need a way to "message" items to other guild members

By "message" I mean, a way to give / trade items even if receiver not on-line

Trade: requires both players on-line at same time
Guild Hall Storage Vault: still a very long way off (we're a PvE only guild)

The problem: My guild, whilst small, has members from many different timezones and so many members never are on-line at the same time. I would like to foster a sense of working together within the guild. We have a guild web site (forum) and so was thinking they could post lists of say weapons or crafter materials they have but don't need, and so could give to / trade with other guild members (example: Warrior with lots of Wood Planks posts "I got 20 Wood Planks, anyone need them?" and a Ranger would read this and reply, "Yes please", that sort of thing).

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EDIT: Sorry, posted in wrong place, just found there's a board dedicated to game improvement discussions, so posted this thread in it's entirety here instead. (Perhaps admins should delete this one, don't seem to have the option to do so myself).