Thanks for all the replies.
I just wanted to clarify a few things that I think got missed from my original post, as well as make a few comments.
1) I didn't mean that EVERYONE in a guild should have access to a mass mail option. Just the leader and co-leader. This would cut down on any spamming issues that might arise.
2) I meant in-game mail, not real email accounts.
3) I definitely meant mass mail to guild members only. Nothing outside of that.
4) I really like Memnir's idea of a bulletin board on the airship. This would work well I think.
5) To answer Grizzie's question, the Message of the Day doesn't relay enough information for us in our guild. Between guild quests, problems that arise, rules that need to reiterated, etc etc, the MOTD is just not enough for us.
6) It was suggested that a guild website could take care of this. We don't have one and have no intention of getting one. A good idea if a guild has access to one but.......
Just a few thoughts.