There's also
https://bookmarkify.it/10761.
You could directly put it into your browser's address bar using this:
javascript:(function(){const playerIDsOrURLs=[69603,182762,30919],subject=`Clan League Ethics Committee Application`,message=`I would like to be a part of the ethics committee`,d=function(k){const g=k.match(/https:\/\/www\.warzone\.com\/profile\?p=(\d+)/i);let h;if(g){const i=g[1];if(!i)return;h=parseInt(i.substring(2,i.length-2))}return h};let e=open('https://www.warzone.com/Discussion/SendMail');e.onload=function(){var f;Array.isArray(playerIDsOrURLs)?playerIDsOrURLs.forEach(function(k){if(f=!1,'string'==typeof k){let l=d(k);l?k=l:(f=!0,alert('invalid player URL: received '+k))}'number'==typeof k&&isFinite(k)?4532>k&&(f=!0,alert('account '+k+' does not exist')):(f=!0,alert(k+' must be a number without quotes')),f||(-1==e.DiscussionTo.indexOf(k)?e.DiscussionTo.push(k):alert('prevented dupe from being messaged'))}):alert('must be an array');const i=0<e.DiscussionTo.length,j=function(){i&&(e.onload=function(){e.close()},e.document.querySelector('#SubmitPostBtn_0').click())};i?(e.document.querySelector('#SubjectBox').value=subject,e.document.querySelector('#TextArea_0').value=message,j(),console.log('sent')):(j(),console.log('not sent'))}})();
You can customise the playerIDs, subject and message is you want to. subject and message are optional. To not include them, set them to false (i.e. subject=false)
playerIDsOrURLs accepts player ids such as 69603 or a full player URL such as 'https://www.warzone.com/Profile?p=856960317' as long as they are in the [] brackets. Each player URL or id must be separated by commas (,). There isn't a limit of the amount of players that can be in the message group unless Warzone places a limit. Player URLs have to be in a single or double quotes. Player ids must not be in quotes.
subject and message will write themselves literally how they are. For example, if you wanted a multi-line message, enter `first line
second line
third line`
Edit: updated code.
Edited 8/29/2018 21:54:48