Mass message sender is a user group that allows users to send messages to multiple users at once, from the MediaWiki message delivery bot account. Further user documentation can be found at m:MassMessage and mw:Help:Extension:MassMessage.
Mass messages should only be sent to groups of users who are likely to want their attention drawn to the message. A prime example is notifying members of a WikiProject about local events or edit-a-thons, though for any regular mailings users should be informed of how they can unsubscribe from future messages (see below).
For other cases, less personalized means of communication are preferred. Wikipedia's primary means of communication is through posts on article talk pages, Wikipedia talk pages, or various noticeboards, including the Village Pump. Editors who are interested in a given topic may have the corresponding page on their watchlist. The requests for comment process can be used to increase participation in a discussion.
To reach the members of a given WikiProject, a post on that project's talk page can be used. Site-wide notices are used for messages of importance to a great many users. Geo-notices are used for locally significant messages.
Adherence to the talk page guidelines is important with mass messages as it can affect a large group of users. Formatting standards should be given consideration, being that verbose, overly formatted and especially large messages may clutter the user's talk page. Formatting is not discouraged however; for invitations to local events, such as an edit-a-thon, it is common to include an image and attractive styling to encourage participation.
The guideline on canvassing is especially relevant to this tool and users should familiarize themselves with its provisions before sending out mass notifications.
Requests for mailings may be made on the talk page; or directly to any of the 1,081 users or administrators with the needed userright. The request page is rarely back logged and is ideal if you are requesting a future-dated message.
Please have the following things available before making your request:
If you wish to opt-out of future mailings, please remove yourself from [[«YOUR MAILING LIST»|the mailing list]] or alternatively to opt-out of all [[Wikipedia:Mass message senders|massmessage mailings]], you may add [[:Category:Wikipedians who opt out of message delivery]] to your user talk page.
Once your request has been answered, you may follow the progress of your request:
If you wish to request mass message sending rights for yourself, please see Wikipedia:Requests for permissions/Mass message sender. Administrators do not need to request or add this user right for themselves or other administrators as it is automatically granted as part of the administrator tools package.
In general, this user right is only granted to those who regularly request mass mailings or otherwise have shown a need for it, and removed from users that are completely inactive. For evaluation purposes, it is good measure to have filed at least one request for mass message delivery exemplifying an understanding of the guidance for use.