diff --git a/funnel/forms/sync_ticket.py b/funnel/forms/sync_ticket.py
index fae507f95..1682820a5 100644
--- a/funnel/forms/sync_ticket.py
+++ b/funnel/forms/sync_ticket.py
@@ -175,8 +175,8 @@ class TicketParticipantForm(forms.Form):
     )
     email = forms.EmailField(
         __("Email"),
-        validators=[forms.validators.DataRequired(), forms.validators.ValidEmail()],
-        filters=[forms.filters.strip()],
+        validators=[forms.validators.Optional(), forms.validators.ValidEmail()],
+        filters=[forms.filters.none_if_empty()],
     )
     phone = forms.StringField(
         __("Phone number"),
@@ -219,6 +219,9 @@ def set_queries(self) -> None:
     def validate(self, *args, **kwargs) -> bool:
         """Validate form."""
         result = super().validate(*args, **kwargs)
+        if self.email.data is None:
+            self.user = None
+            return True
         with db.session.no_autoflush:
             accountemail = AccountEmail.get(email=self.email.data)
             if accountemail is not None:
diff --git a/funnel/models/sync_ticket.py b/funnel/models/sync_ticket.py
index d51940425..29f99708d 100644
--- a/funnel/models/sync_ticket.py
+++ b/funnel/models/sync_ticket.py
@@ -207,7 +207,7 @@ class TicketParticipant(EmailAddressMixin, UuidMixin, BaseMixin, Model):
     """A participant in one or more events, synced from an external ticket source."""
 
     __tablename__ = 'ticket_participant'
-    __email_optional__ = False
+    __email_optional__ = True
     __email_for__ = 'participant'
 
     fullname = with_roles(
@@ -376,7 +376,9 @@ def checkin_list(cls, ticket_event: TicketEvent) -> list:  # TODO: List type?
                 TicketEventParticipant,
                 TicketParticipant.id == TicketEventParticipant.ticket_participant_id,
             )
-            .join(EmailAddress, EmailAddress.id == TicketParticipant.email_address_id)
+            .outerjoin(
+                EmailAddress, EmailAddress.id == TicketParticipant.email_address_id
+            )
             .outerjoin(
                 SyncTicket, TicketParticipant.id == SyncTicket.ticket_participant_id
             )
diff --git a/funnel/views/ticket_participant.py b/funnel/views/ticket_participant.py
index 126d300b6..d788a22b3 100644
--- a/funnel/views/ticket_participant.py
+++ b/funnel/views/ticket_participant.py
@@ -96,7 +96,9 @@ def ticket_participant_checkin_data(ticket_participant, project, ticket_event):
         'puuid_b58': puuid_b58,
         'fullname': ticket_participant.fullname,
         'company': ticket_participant.company,
-        'email': mask_email(ticket_participant.email),
+        'email': mask_email(ticket_participant.email)
+        if ticket_participant.email
+        else None,
         'badge_printed': ticket_participant.badge_printed,
         'checked_in': ticket_participant.checked_in,
         'ticket_type_titles': ticket_participant.ticket_type_titles,
diff --git a/migrations/versions/017c60414c03_make_ticket_participant_email_optional.py b/migrations/versions/017c60414c03_make_ticket_participant_email_optional.py
new file mode 100644
index 000000000..e10c3250b
--- /dev/null
+++ b/migrations/versions/017c60414c03_make_ticket_participant_email_optional.py
@@ -0,0 +1,44 @@
+"""Make ticket participant email optional.
+
+Revision ID: 017c60414c03
+Revises: 4f9ca10b7b9d
+Create Date: 2023-10-05 15:08:34.540672
+
+"""
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = '017c60414c03'
+down_revision: str = '4f9ca10b7b9d'
+branch_labels: str | tuple[str, ...] | None = None
+depends_on: str | tuple[str, ...] | None = None
+
+
+def upgrade(engine_name: str = '') -> None:
+    """Upgrade all databases."""
+    # Do not modify. Edit `upgrade_` instead
+    globals().get(f'upgrade_{engine_name}', lambda: None)()
+
+
+def downgrade(engine_name: str = '') -> None:
+    """Downgrade all databases."""
+    # Do not modify. Edit `downgrade_` instead
+    globals().get(f'downgrade_{engine_name}', lambda: None)()
+
+
+def upgrade_() -> None:
+    """Upgrade default database."""
+    with op.batch_alter_table('ticket_participant', schema=None) as batch_op:
+        batch_op.alter_column(
+            'email_address_id', existing_type=sa.INTEGER(), nullable=True
+        )
+
+
+def downgrade_() -> None:
+    """Downgrade default database."""
+    with op.batch_alter_table('ticket_participant', schema=None) as batch_op:
+        batch_op.alter_column(
+            'email_address_id', existing_type=sa.INTEGER(), nullable=False
+        )