Update docs to mirror the server readme

Saw it mentioned in parse-community/parse-server#275 a few times, and took me a while to find it, so updating here too. Not sure what the longer term plans are regarding docs, seems to be multiple places for the same docs

Author: James

_includes/parse-server/compatibility.md

@@ -181,4 +181,78 @@ Facebook, Twitter, and Anonymous logins are supported out of the box. Support fo
 
 ## Welcome Emails and Email Verification
 
-This is not supported out of the box. But, you can use a `beforeSave` to send out emails using a provider like Mailgun and add logic for verification. [Subscribe to this issue](https://github.com/parse-community/parse-server/issues/275) to be notified if email verification support is added to Parse Server.
+Verifying user email addresses and enabling password reset via email requires an email adapter. As part of the `parse-server` package we provide an adapter for sending email through Mailgun. To use it, sign up for Mailgun, and add this to your initialization code:
+
+```js
+var server = ParseServer({
+  ...otherOptions,
+  // Enable email verification
+  verifyUserEmails: true,
+
+  // if `verifyUserEmails` is `true` and
+  //     if `emailVerifyTokenValidityDuration` is `undefined` then
+  //        email verify token never expires
+  //     else
+  //        email verify token expires after `emailVerifyTokenValidityDuration`
+  //
+  // `emailVerifyTokenValidityDuration` defaults to `undefined`
+  //
+  // email verify token below expires in 2 hours (= 2 * 60 * 60 == 7200 seconds)
+  emailVerifyTokenValidityDuration: 2 * 60 * 60, // in seconds (2 hours = 7200 seconds)
+
+  // set preventLoginWithUnverifiedEmail to false to allow user to login without verifying their email
+  // set preventLoginWithUnverifiedEmail to true to prevent user from login if their email is not verified
+  preventLoginWithUnverifiedEmail: false, // defaults to false
+
+  // The public URL of your app.
+  // This will appear in the link that is used to verify email addresses and reset passwords.
+  // Set the mount path as it is in serverURL
+  publicServerURL: 'https://example.com/parse',
+  // Your apps name. This will appear in the subject and body of the emails that are sent.
+  appName: 'Parse App',
+  // The email adapter
+  emailAdapter: {
+    module: '@parse/simple-mailgun-adapter',
+    options: {
+      // The address that your emails come from
+      fromAddress: '[email protected]',
+      // Your domain from mailgun.com
+      domain: 'example.com',
+      // Your API key from mailgun.com
+      apiKey: 'key-mykey',
+    }
+  },
+
+  // account lockout policy setting (OPTIONAL) - defaults to undefined
+  // if the account lockout policy is set and there are more than `threshold` number of failed login attempts then the `login` api call returns error code `Parse.Error.OBJECT_NOT_FOUND` with error message `Your account is locked due to multiple failed login attempts. Please try again after <duration> minute(s)`. After `duration` minutes of no login attempts, the application will allow the user to try login again.
+  accountLockout: {
+    duration: 5, // duration policy setting determines the number of minutes that a locked-out account remains locked out before automatically becoming unlocked. Set it to a value greater than 0 and less than 100000.
+    threshold: 3, // threshold policy setting determines the number of failed sign-in attempts that will cause a user account to be locked. Set it to an integer value greater than 0 and less than 1000.
+  },
+  // optional settings to enforce password policies
+  passwordPolicy: {
+    // Two optional settings to enforce strong passwords. Either one or both can be specified. 
+    // If both are specified, both checks must pass to accept the password
+    // 1. a RegExp object or a regex string representing the pattern to enforce 
+    validatorPattern: /^(?=.*[a-z])(?=.*[A-Z])(?=.*[0-9])(?=.{8,})/, // enforce password with at least 8 char with at least 1 lower case, 1 upper case and 1 digit
+    // 2. a callback function to be invoked to validate the password  
+    validatorCallback: (password) => { return validatePassword(password) }, 
+    doNotAllowUsername: true, // optional setting to disallow username in passwords
+    maxPasswordAge: 90, // optional setting in days for password expiry. Login fails if user does not reset the password within this period after signup/last reset. 
+    maxPasswordHistory: 5, // optional setting to prevent reuse of previous n passwords. Maximum value that can be specified is 20. Not specifying it or specifying 0 will not enforce history.
+    //optional setting to set a validity duration for password reset links (in seconds)
+    resetTokenValidityDuration: 24*60*60, // expire after 24 hours
+  }
+});
+```
+
+You can also use other email adapters contributed by the community such as:
+- [parse-server-postmark-adapter](https://www.npmjs.com/package/parse-server-postmark-adapter)
+- [parse-server-sendgrid-adapter](https://www.npmjs.com/package/parse-server-sendgrid-adapter)
+- [parse-server-mandrill-adapter](https://www.npmjs.com/package/parse-server-mandrill-adapter)
+- [parse-server-simple-ses-adapter](https://www.npmjs.com/package/parse-server-simple-ses-adapter)
+- [parse-server-mailgun-adapter-template](https://www.npmjs.com/package/parse-server-mailgun-adapter-template)
+- [parse-server-sendinblue-adapter](https://www.npmjs.com/package/parse-server-sendinblue-adapter)
+- [parse-server-mailjet-adapter](https://www.npmjs.com/package/parse-server-mailjet-adapter)
+- [simple-parse-smtp-adapter](https://www.npmjs.com/package/simple-parse-smtp-adapter)
+- [parse-server-generic-email-adapter](https://www.npmjs.com/package/parse-server-generic-email-adapter)