diff --git a/src/middlewared/middlewared/plugins/mail.py b/src/middlewared/middlewared/plugins/mail.py
index 8ec96feb7c650..e09be97ad0d08 100644
--- a/src/middlewared/middlewared/plugins/mail.py
+++ b/src/middlewared/middlewared/plugins/mail.py
@@ -28,15 +28,13 @@ class DenyNetworkActivity(Exception):
     pass
 
 
-class QueueItem(object):
-
+class QueueItem:
     def __init__(self, message):
         self.attempts = 0
         self.message = message
 
 
-class MailQueue(object):
-
+class MailQueue:
     MAX_ATTEMPTS = 3
     MAX_QUEUE_LIMIT = 20
 
@@ -73,10 +71,7 @@ class MailModel(sa.Model):
 
 
 class MailService(ConfigService):
-
     mail_queue = MailQueue()
-    oauth_access_token = None
-    oauth_access_token_expires_at = None
 
     class Config:
         datastore = 'system.email'
@@ -96,6 +91,7 @@ class Config:
         Password('pass', null=True, required=True),
         Dict(
             'oauth',
+            Str('provider'),
             Str('client_id'),
             Str('client_secret'),
             Password('refresh_token'),
@@ -119,6 +115,7 @@ async def mail_extend(self, cfg):
             (
                 'replace', Dict(
                     'oauth',
+                    Str('provider'),
                     Str('client_id', required=True),
                     Str('client_secret', required=True),
                     Password('refresh_token', required=True),
@@ -370,7 +367,7 @@ def read_json():
                 msg[key] = val
 
         try:
-            if config['oauth']:
+            if config['oauth'] and config['oauth']['provider'] == 'gmail':
                 self.middleware.call_sync('mail.gmail_send', msg, config)
             else:
                 server = self._get_smtp_server(config, message['timeout'], local_hostname=local_hostname)
@@ -429,7 +426,9 @@ def _get_smtp_server(self, config, timeout=300, local_hostname=None):
                 local_hostname=local_hostname)
             if config['security'] == 'TLS':
                 server.starttls()
-        if config['smtp']:
+        if config['oauth'] and config['oauth']['provider'] == 'outlook':
+            self.middleware.call_sync('mail.outlook_xoauth2', server, config)
+        elif config['smtp']:
             server.login(config['user'], config['pass'])
 
         return server
@@ -441,7 +440,7 @@ def send_mail_queue(self):
             for queue in list(mq.queue):
                 try:
                     config = self.middleware.call_sync('mail.config')
-                    if config['oauth']:
+                    if config['oauth'] and config['oauth']['provider'] == 'gmail':
                         self.middleware.call_sync('mail.gmail_send', queue.message, config)
                     else:
                         server = self._get_smtp_server(config)
diff --git a/src/middlewared/middlewared/plugins/mail_/gmail.py b/src/middlewared/middlewared/plugins/mail_/gmail.py
index e211742fe4544..549fccf26000d 100644
--- a/src/middlewared/middlewared/plugins/mail_/gmail.py
+++ b/src/middlewared/middlewared/plugins/mail_/gmail.py
@@ -59,7 +59,7 @@ def gmail_initialize(self):
 
     @private
     def gmail_build_service(self, config):
-        if config["oauth"]:
+        if config["oauth"] and config["oauth"]["provider"] == "gmail":
             return GmailService(config)
 
         return None
diff --git a/src/middlewared/middlewared/plugins/mail_/outlook.py b/src/middlewared/middlewared/plugins/mail_/outlook.py
new file mode 100644
index 0000000000000..40c97e951c9ae
--- /dev/null
+++ b/src/middlewared/middlewared/plugins/mail_/outlook.py
@@ -0,0 +1,67 @@
+import base64
+from dataclasses import dataclass
+from smtplib import SMTP
+import time
+
+import requests
+
+from middlewared.service import CallError, private, Service
+
+
+@dataclass
+class OutlookToken:
+    token: str
+    expires_at: float
+
+
+class MailService(Service):
+    outlook_tokens: dict[str, OutlookToken] = {}
+
+    @private
+    def outlook_xoauth2(self, server: SMTP, config: dict):
+        server.ehlo()
+
+        if token := self._get_outlook_token(config["fromemail"], config["oauth"]["refresh_token"]):
+            code, response = self._do_xoauth2(server, config["fromemail"], token)
+            if 200 <= code <= 299:
+                return
+
+            self.logger.warning("Outlook XOAUTH2 failed: %r %r. Refreshing access token", code, response)
+
+        self.logger.debug("Requesting Outlook access token")
+        r = requests.post(
+            "https://login.microsoftonline.com/common/oauth2/v2.0/token",
+            data={
+                "grant_type": "refresh_token",
+                "client_id": config["oauth"]["client_id"],
+                "client_secret": config["oauth"]["client_secret"],
+                "refresh_token": config["oauth"]["refresh_token"],
+                "scope": "https://outlook.office.com/SMTP.Send openid offline_access",
+            }
+        )
+        r.raise_for_status()
+        response = r.json()
+
+        token = response["access_token"]
+        self._set_outlook_token(config["fromemail"], config["oauth"]["refresh_token"], token, response["expires_in"])
+
+        code, response = self._do_xoauth2(server, config["fromemail"], token)
+        if 200 <= code <= 299:
+            return
+
+        raise CallError("Outlook XOAUTH2 failed: %r %r" % (code, response))
+
+    def _get_outlook_token(self, email: str, refresh_token: str) -> str | None:
+        for key, token in list(self.outlook_tokens.items()):
+            if token.expires_at < time.monotonic() - 5:
+                self.outlook_tokens.pop(key)
+
+        if token := self.outlook_tokens.get(email + refresh_token):
+            return token.token
+
+    def _set_outlook_token(self, email: str, refresh_token: str, token: str, expires_in: int):
+        self.outlook_tokens[email + refresh_token] = OutlookToken(token, time.monotonic() + expires_in)
+
+    def _do_xoauth2(self, server: SMTP, email: str, access_token: str):
+        auth_string = f"user={email}\1auth=Bearer {access_token}\1\1"
+        return server.docmd("AUTH XOAUTH2", base64.b64encode(auth_string.encode()).decode())