diff --git a/changelog.d/3662.feature b/changelog.d/3662.feature
new file mode 100644
index 000000000..daacef086
--- /dev/null
+++ b/changelog.d/3662.feature
@@ -0,0 +1 @@
+Ability to whitelist specific threepids against monthly active user limiting
diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index 3a67db8b3..a4a65e728 100755
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -518,6 +518,8 @@ def run(hs):
     # If you increase the loop period, the accuracy of user_daily_visits
     # table will decrease
     clock.looping_call(generate_user_daily_visit_stats, 5 * 60 * 1000)
+
+    # monthly active user limiting functionality
     clock.looping_call(
         hs.get_datastore().reap_monthly_active_users, 1000 * 60 * 60
     )
@@ -530,9 +532,13 @@ def run(hs):
         current_mau_gauge.set(float(count))
         max_mau_value_gauge.set(float(hs.config.max_mau_value))
 
+    hs.get_datastore().initialise_reserved_users(
+        hs.config.mau_limits_reserved_threepids
+    )
     generate_monthly_active_users()
     if hs.config.limit_usage_by_mau:
         clock.looping_call(generate_monthly_active_users, 5 * 60 * 1000)
+    # End of monthly active user settings
 
     if hs.config.report_stats:
         logger.info("Scheduling stats reporting for 3 hour intervals")
diff --git a/synapse/config/server.py b/synapse/config/server.py
index 2e1e2f596..3b078d72c 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -74,6 +74,9 @@ class ServerConfig(Config):
             self.max_mau_value = config.get(
                 "max_mau_value", 0,
             )
+        self.mau_limits_reserved_threepids = config.get(
+            "mau_limit_reserved_threepids", []
+        )
 
         # Options to disable HS
         self.hs_disabled = config.get("hs_disabled", False)
diff --git a/synapse/storage/monthly_active_users.py b/synapse/storage/monthly_active_users.py
index 8b3beaf26..d47dcef3a 100644
--- a/synapse/storage/monthly_active_users.py
+++ b/synapse/storage/monthly_active_users.py
@@ -12,6 +12,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import logging
 
 from twisted.internet import defer
 
@@ -19,6 +20,8 @@ from synapse.util.caches.descriptors import cached
 
 from ._base import SQLBaseStore
 
+logger = logging.getLogger(__name__)
+
 # Number of msec of granularity to store the monthly_active_user timestamp
 # This means it is not necessary to update the table on every request
 LAST_SEEN_GRANULARITY = 60 * 60 * 1000
@@ -29,7 +32,29 @@ class MonthlyActiveUsersStore(SQLBaseStore):
         super(MonthlyActiveUsersStore, self).__init__(None, hs)
         self._clock = hs.get_clock()
         self.hs = hs
+        self.reserved_users = ()
 
+    @defer.inlineCallbacks
+    def initialise_reserved_users(self, threepids):
+        # TODO Why can't I do this in init?
+        store = self.hs.get_datastore()
+        reserved_user_list = []
+
+        # Do not add more reserved users than the total allowable number
+        for tp in threepids[:self.hs.config.max_mau_value]:
+            user_id = yield store.get_user_id_by_threepid(
+                tp["medium"], tp["address"]
+            )
+            if user_id:
+                self.upsert_monthly_active_user(user_id)
+                reserved_user_list.append(user_id)
+            else:
+                logger.warning(
+                    "mau limit reserved threepid %s not found in db" % tp
+                )
+        self.reserved_users = tuple(reserved_user_list)
+
+    @defer.inlineCallbacks
     def reap_monthly_active_users(self):
         """
         Cleans out monthly active user table to ensure that no stale
@@ -44,8 +69,20 @@ class MonthlyActiveUsersStore(SQLBaseStore):
                 int(self._clock.time_msec()) - (1000 * 60 * 60 * 24 * 30)
             )
             # Purge stale users
-            sql = "DELETE FROM monthly_active_users WHERE timestamp < ?"
-            txn.execute(sql, (thirty_days_ago,))
+
+            # questionmarks is a hack to overcome sqlite not supporting
+            # tuples in 'WHERE IN %s'
+            questionmarks = '?' * len(self.reserved_users)
+            query_args = [thirty_days_ago]
+            query_args.extend(self.reserved_users)
+
+            sql = """
+                DELETE FROM monthly_active_users
+                WHERE timestamp < ?
+                AND user_id NOT IN ({})
+                """.format(','.join(questionmarks))
+
+            txn.execute(sql, query_args)
 
             # If MAU user count still exceeds the MAU threshold, then delete on
             # a least recently active basis.
@@ -55,6 +92,8 @@ class MonthlyActiveUsersStore(SQLBaseStore):
             # While Postgres does not require 'LIMIT', but also does not support
             # negative LIMIT values. So there is no way to write it that both can
             # support
+            query_args = [self.hs.config.max_mau_value]
+            query_args.extend(self.reserved_users)
             sql = """
                 DELETE FROM monthly_active_users
                 WHERE user_id NOT IN (
@@ -62,8 +101,9 @@ class MonthlyActiveUsersStore(SQLBaseStore):
                     ORDER BY timestamp DESC
                     LIMIT ?
                     )
-                """
-            txn.execute(sql, (self.hs.config.max_mau_value,))
+                AND user_id NOT IN ({})
+                """.format(','.join(questionmarks))
+            txn.execute(sql, query_args)
 
         yield self.runInteraction("reap_monthly_active_users", _reap_users)
         # It seems poor to invalidate the whole cache, Postgres supports
@@ -122,7 +162,7 @@ class MonthlyActiveUsersStore(SQLBaseStore):
             Arguments:
                 user_id (str): user to add/update
             Return:
-                int : timestamp since last seen, None if never seen
+                Deferred[int] : timestamp since last seen, None if never seen
 
         """
 
@@ -144,7 +184,6 @@ class MonthlyActiveUsersStore(SQLBaseStore):
         Args:
             user_id(str): the user_id to query
         """
-
         if self.hs.config.limit_usage_by_mau:
             last_seen_timestamp = yield self._user_last_seen_monthly_active(user_id)
             now = self.hs.get_clock().time_msec()
diff --git a/tests/storage/test_monthly_active_users.py b/tests/storage/test_monthly_active_users.py
index 0bfd24a7f..cbd480cd4 100644
--- a/tests/storage/test_monthly_active_users.py
+++ b/tests/storage/test_monthly_active_users.py
@@ -19,6 +19,8 @@ import tests.unittest
 import tests.utils
 from tests.utils import setup_test_homeserver
 
+FORTY_DAYS = 40 * 24 * 60 * 60
+
 
 class MonthlyActiveUsersTestCase(tests.unittest.TestCase):
     def __init__(self, *args, **kwargs):
@@ -29,6 +31,56 @@ class MonthlyActiveUsersTestCase(tests.unittest.TestCase):
         self.hs = yield setup_test_homeserver()
         self.store = self.hs.get_datastore()
 
+    @defer.inlineCallbacks
+    def test_initialise_reserved_users(self):
+
+        user1 = "@user1:server"
+        user1_email = "user1@matrix.org"
+        user2 = "@user2:server"
+        user2_email = "user2@matrix.org"
+        threepids = [
+            {'medium': 'email', 'address': user1_email},
+            {'medium': 'email', 'address': user2_email}
+        ]
+        user_num = len(threepids)
+
+        yield self.store.register(
+            user_id=user1,
+            token="123",
+            password_hash=None)
+
+        yield self.store.register(
+            user_id=user2,
+            token="456",
+            password_hash=None)
+
+        now = int(self.hs.get_clock().time_msec())
+        yield self.store.user_add_threepid(user1, "email", user1_email, now, now)
+        yield self.store.user_add_threepid(user2, "email", user2_email, now, now)
+        yield self.store.initialise_reserved_users(threepids)
+
+        active_count = yield self.store.get_monthly_active_count()
+
+        # Test total counts
+        self.assertEquals(active_count, user_num)
+
+        # Test user is marked as active
+
+        timestamp = yield self.store._user_last_seen_monthly_active(user1)
+        self.assertTrue(timestamp)
+        timestamp = yield self.store._user_last_seen_monthly_active(user2)
+        self.assertTrue(timestamp)
+
+        # Test that users are never removed from the db.
+        self.hs.config.max_mau_value = 0
+
+        self.hs.get_clock().advance_time(FORTY_DAYS)
+
+        yield self.store.reap_monthly_active_users()
+
+        active_count = yield self.store.get_monthly_active_count()
+        self.assertEquals(active_count, user_num)
+
     @defer.inlineCallbacks
     def test_can_insert_and_count_mau(self):
         count = yield self.store.get_monthly_active_count()
@@ -63,4 +115,9 @@ class MonthlyActiveUsersTestCase(tests.unittest.TestCase):
         self.assertTrue(count, initial_users)
         yield self.store.reap_monthly_active_users()
         count = yield self.store.get_monthly_active_count()
-        self.assertTrue(count, initial_users - self.hs.config.max_mau_value)
+        self.assertEquals(count, initial_users - self.hs.config.max_mau_value)
+
+        self.hs.get_clock().advance_time(FORTY_DAYS)
+        yield self.store.reap_monthly_active_users()
+        count = yield self.store.get_monthly_active_count()
+        self.assertEquals(count, 0)
diff --git a/tests/utils.py b/tests/utils.py
index a0aa38d26..5e4d77920 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -76,6 +76,8 @@ def setup_test_homeserver(name="test", datastore=None, config=None, reactor=None
         config.limit_usage_by_mau = False
         config.hs_disabled = False
         config.hs_disabled_message = ""
+        config.max_mau_value = 50
+        config.mau_limits_reserved_threepids = []
 
         # disable user directory updates, because they get done in the
         # background, which upsets the test runner.