Send one message to multiple recipients with Auto Message!
You can
-Input a list of userIDs to send a mail to
-Select a guild to message
-Select individual or multiple ranks of a guild
-Exclude members via Note (enable "Note Immunity" to ignore all members with a note on their name)
-Add dynamic text to your message to automatically include the guild name if you message players of multiple guilds at once
AutoMessage won't send a player a duplicate mail if they are in multiple guilds you selected
This addon sends one mail every 1,6 seconds (basically as fast as the server will allow).
You can specify an unlimited amount of recipients in the addon settings.