diff --git a/joint_teapot/app.py b/joint_teapot/app.py
index ca34ccf..c0bc0bb 100644
--- a/joint_teapot/app.py
+++ b/joint_teapot/app.py
@@ -242,6 +242,13 @@ def create_personal_channels_on_mm(
 ) -> None:
     tea.pot.create_channels_for_individuals(invite_teaching_team)
 
+@app.command(
+    "invite-students-to-mm-team",
+    help="invite all canvas students to the mattermost team",
+)
+def invite_students_to_mattermost_team() -> None:
+    tea.pot.invite_students_to_mattermost_team()
+
 
 @app.command(
     "create-webhooks-for-mm",
diff --git a/joint_teapot/teapot.py b/joint_teapot/teapot.py
index d2954e3..f2494a3 100644
--- a/joint_teapot/teapot.py
+++ b/joint_teapot/teapot.py
@@ -231,6 +231,9 @@ class Teapot:
             self.canvas.students, invite_teaching_teams
         )
 
+    def invite_students_to_mattermost_team(self) -> None:
+        return self.mattermost.invite_students_to_team(self.canvas.students)
+
     def joj3_post_issue(
         self,
         env: joj3.Env,
diff --git a/joint_teapot/workers/canvas.py b/joint_teapot/workers/canvas.py
index 641b8af..2ba1782 100644
--- a/joint_teapot/workers/canvas.py
+++ b/joint_teapot/workers/canvas.py
@@ -39,8 +39,19 @@ class Canvas:
             student.name = (
                 re.sub(r"[^\x00-\x7F]+", "", student.name).strip().title()
             )  # We only care english name
-            student.sis_id = student.login_id
-            student.login_id = student.email.split("@")[0]
+            # Some users (like system users, announcers) might not have login_id
+            if hasattr(student, 'login_id') and student.login_id:
+                student.sis_id = student.login_id
+                student.login_id = student.email.split("@")[0]
+            else:
+                # For users without login_id, use email prefix as both sis_id and login_id
+                if hasattr(student, 'email') and student.email:
+                    student.login_id = student.email.split("@")[0]
+                    student.sis_id = student.login_id
+                else:
+                    # Fallback for users without email
+                    student.login_id = f"user_{student.id}"
+                    student.sis_id = student.login_id
             return student
 
         self.students = [
diff --git a/joint_teapot/workers/mattermost.py b/joint_teapot/workers/mattermost.py
index 93cc47d..a96721b 100644
--- a/joint_teapot/workers/mattermost.py
+++ b/joint_teapot/workers/mattermost.py
@@ -7,6 +7,7 @@ from mattermostdriver import Driver
 from joint_teapot.config import settings
 from joint_teapot.utils.logger import logger
 from joint_teapot.workers.gitea import Gitea
+from joint_teapot.workers.canvas import User
 
 
 class Mattermost:
@@ -229,14 +230,21 @@ class Mattermost:
                 logger.warning(f"Error when creating outgoing webhook at Gitea: {e}")
 
     # unused since we can give students invitation links instead
-    def invite_students_to_team(self, students: List[str]) -> None:
+    def invite_students_to_team(self, students: List[User]) -> None:
         for student in students:
+            username = student.login_id
+
+            if not username:
+                student_id = getattr(student, 'id', 'unknown')
+                logger.warning(f"Student {student_id} has no login_id, skipping")
+                continue
+
             try:
-                mmuser = self.endpoint.users.get_user_by_username(student)
+                mmuser = self.endpoint.users.get_user_by_username(username)
             except Exception:
-                logger.warning(f"User {student} is not found on the Mattermost server")
+                logger.warning(f"User {username} is not found on the Mattermost server")
                 continue
             self.endpoint.teams.add_user_to_team(
                 self.team["id"], {"user_id": mmuser["id"], "team_id": self.team["id"]}
             )
-            logger.info(f"Added user {student} to team {self.team['name']}")
+            logger.info(f"Added user {username} to team {self.team['name']}")