diff --git a/CHANGELOG.md b/CHANGELOG.md
index 876f17d..ff6fe58 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Test connection always showed success; add per-account test endpoint
   ([`441e8b5`](https://github.com/christianlouis/InboxConverge/commit/441e8b54e958686fe52414393d715a18dfcda77c))
+- Fixed 21 mypy type errors across `notification_service.py`, `mail_processor.py`, `auth.py`, `tasks.py`, `providers.py`, `mail_accounts.py`, and `main.py`
 
 
 ## v0.3.0 (2026-03-28)
diff --git a/backend/app/api/v1/endpoints/auth.py b/backend/app/api/v1/endpoints/auth.py
index d60ace9..a6420aa 100644
--- a/backend/app/api/v1/endpoints/auth.py
+++ b/backend/app/api/v1/endpoints/auth.py
@@ -153,13 +153,13 @@ async def login(
 
     # Domain restriction — superusers always bypass
     if not user.is_superuser:
-        _check_domain_allowed(user.email)
+        _check_domain_allowed(str(user.email))
 
     # Update last login
     user.last_login_at = datetime.now(timezone.utc)  # type: ignore[assignment]
 
     # Auto-promote to superuser if this is the configured admin email
-    if not user.is_superuser and _is_admin_email(user.email):
+    if not user.is_superuser and _is_admin_email(str(user.email)):
         user.is_superuser = True  # type: ignore[assignment]
         logger.info(f"Auto-promoted admin user: {user.email}")
 
diff --git a/backend/app/api/v1/endpoints/mail_accounts.py b/backend/app/api/v1/endpoints/mail_accounts.py
index 4e73ba7..3d870f4 100644
--- a/backend/app/api/v1/endpoints/mail_accounts.py
+++ b/backend/app/api/v1/endpoints/mail_accounts.py
@@ -75,7 +75,7 @@ async def create_mail_account(
                 "pro": settings.TIER_PRO_MAX_ACCOUNTS,
                 "enterprise": settings.TIER_ENTERPRISE_MAX_ACCOUNTS,
             }
-            max_accounts = tier_limits.get(current_user.subscription_tier.value, 1)
+            max_accounts = tier_limits.get(current_user.subscription_tier.value, 1)  # type: ignore[assignment]
 
         if len(existing_accounts) >= max_accounts:
             raise HTTPException(
@@ -320,7 +320,7 @@ async def test_existing_mail_connection(
         )
 
     try:
-        password = decrypt_credential(account.encrypted_password)
+        password = decrypt_credential(str(account.encrypted_password))
     except Exception:
         raise HTTPException(
             status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
diff --git a/backend/app/api/v1/endpoints/providers.py b/backend/app/api/v1/endpoints/providers.py
index 1757b87..5d814db 100644
--- a/backend/app/api/v1/endpoints/providers.py
+++ b/backend/app/api/v1/endpoints/providers.py
@@ -266,7 +266,7 @@ async def save_gmail_credential(
             gmail_email=credential_in.gmail_email,
             encrypted_access_token=encrypted_access,
             encrypted_refresh_token=encrypted_refresh,
-            scopes=build_gmail_credential_scopes(),
+            scopes=build_gmail_credential_scopes(granted_scopes=[]),
             is_valid=True,
             last_verified_at=datetime.now(timezone.utc),
         )
diff --git a/backend/app/main.py b/backend/app/main.py
index 7c689b0..2469c9a 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -36,7 +36,7 @@ logger = logging.getLogger(__name__)
 
 
 @asynccontextmanager
-async def lifespan(app: FastAPI) -> AsyncIterator[None]:
+async def lifespan(_app: FastAPI) -> AsyncIterator[None]:
     """Application lifespan handler for startup and shutdown events."""
     # Startup
     logger.info(f"Starting {settings.APP_NAME} v{settings.APP_VERSION}")
diff --git a/backend/app/services/mail_processor.py b/backend/app/services/mail_processor.py
index 208908f..523d586 100644
--- a/backend/app/services/mail_processor.py
+++ b/backend/app/services/mail_processor.py
@@ -183,18 +183,18 @@ class MailProcessor:
                 if self.account.protocol == MailProtocol.POP3_SSL:
                     context = ssl.create_default_context()
                     pop_conn = poplib.POP3_SSL(
-                        self.account.host,
-                        self.account.port,
+                        str(self.account.host),
+                        int(self.account.port),
                         context=context,
                         timeout=30,
                     )
                 else:
-                    pop_conn = poplib.POP3(
-                        self.account.host, self.account.port, timeout=30
+                    pop_conn = poplib.POP3(  # type: ignore[assignment]
+                        str(self.account.host), int(self.account.port), timeout=30
                     )
 
                 # Authenticate
-                pop_conn.user(self.account.username)
+                pop_conn.user(str(self.account.username))
                 pop_conn.pass_(self.password)
 
                 # Retrieve UIDL map: {msg_number: uid_string}
diff --git a/backend/app/services/notification_service.py b/backend/app/services/notification_service.py
index 5927199..df03532 100644
--- a/backend/app/services/notification_service.py
+++ b/backend/app/services/notification_service.py
@@ -60,7 +60,7 @@ async def send_user_notification(
             continue
 
         try:
-            success = await _send_apprise(config.apprise_url or "", title, body)
+            success = await _send_apprise(str(config.apprise_url or ""), title, body)
             if success:
                 sent += 1
         except Exception as exc:
@@ -99,7 +99,7 @@ async def send_admin_notification(
     sent = 0
     for config in configs:
         try:
-            success = await _send_apprise(config.apprise_url or "", title, body)
+            success = await _send_apprise(str(config.apprise_url or ""), title, body)
             if success:
                 sent += 1
         except Exception as exc:
diff --git a/backend/app/workers/tasks.py b/backend/app/workers/tasks.py
index f0f6c7c..d07eb31 100644
--- a/backend/app/workers/tasks.py
+++ b/backend/app/workers/tasks.py
@@ -137,6 +137,7 @@ async def process_mail_account(account_id: int):
 
             gmail_service = None
             smtp_config = None
+            gmail_cred = None
 
             if use_gmail_api:
                 # Get user's Gmail credentials
@@ -238,7 +239,7 @@ async def process_mail_account(account_id: int):
                 error_msg: str | None = None
 
                 try:
-                    if use_gmail_api and gmail_service:
+                    if use_gmail_api and gmail_service and gmail_cred:
                         # Inject via Gmail API (preferred)
                         label_ids = await gmail_service.build_import_label_ids(
                             import_label_templates=gmail_cred.import_label_templates,
@@ -286,7 +287,7 @@ async def process_mail_account(account_id: int):
                         try:
                             await send_user_notification(
                                 db=db,
-                                user_id=account.user_id,
+                                user_id=int(account.user_id),
                                 title="InboxRescue: Gmail Authorization Expired",
                                 body=f"Your Gmail credentials for account '{account.name}' have been revoked. Please re-authorize Gmail access in Settings.",
                                 notify_on_error=True,
@@ -347,7 +348,7 @@ async def process_mail_account(account_id: int):
             run.emails_failed = emails_failed  # type: ignore[assignment]
             run.completed_at = datetime.now(timezone.utc)  # type: ignore[assignment]
             run.duration_seconds = (
-                run.completed_at - _as_utc(run.started_at)
+                run.completed_at - _as_utc(run.started_at)  # type: ignore[arg-type]
             ).total_seconds()
             run.status = "completed" if emails_failed == 0 else "partial_failure"  # type: ignore[assignment]
 
@@ -366,7 +367,7 @@ async def process_mail_account(account_id: int):
                 try:
                     await send_user_notification(
                         db=db,
-                        user_id=account.user_id,
+                        user_id=int(account.user_id),
                         title="InboxRescue: Mail Forwarding Failures",
                         body=f"Mail account '{account.name}': {emails_failed} email(s) failed to forward.",
                         notify_on_error=True,
@@ -440,7 +441,7 @@ async def process_mail_account(account_id: int):
                     try:
                         await send_user_notification(
                             db=db,
-                            user_id=account.user_id,
+                            user_id=int(account.user_id),
                             title="InboxRescue: Mail Processing Error",
                             body=f"Error processing mail account '{account.name}': {e}",
                             notify_on_error=True,
@@ -488,7 +489,7 @@ async def process_all_enabled_accounts():
                 )
                 stale_run.completed_at = datetime.now(timezone.utc)  # type: ignore[assignment]
                 stale_run.duration_seconds = (  # type: ignore[assignment]
-                    stale_run.completed_at - _as_utc(stale_run.started_at)
+                    stale_run.completed_at - _as_utc(stale_run.started_at)  # type: ignore[arg-type]
                 ).total_seconds()
             if stale_runs:
                 await db.commit()
@@ -571,12 +572,10 @@ async def cleanup_old_logs(days_to_keep: int = 30):
             stale_runs = stale_result.scalars().all()
             for stale_run in stale_runs:
                 stale_run.status = "failed"  # type: ignore[assignment]
-                stale_run.error_message = (  # type: ignore[assignment]
-                    "Run timed out or worker was killed before completion"
-                )
+                stale_run.error_message = "Run timed out or worker was killed before completion"  # type: ignore[assignment]
                 stale_run.completed_at = datetime.now(timezone.utc)  # type: ignore[assignment]
                 stale_run.duration_seconds = (  # type: ignore[assignment]
-                    stale_run.completed_at - _as_utc(stale_run.started_at)
+                    stale_run.completed_at - _as_utc(stale_run.started_at)  # type: ignore[arg-type]
                 ).total_seconds()
 
             if stale_runs:
diff --git a/docs/TODO.md b/docs/TODO.md
index ad3c077..82bca22 100644
--- a/docs/TODO.md
+++ b/docs/TODO.md
@@ -5,6 +5,7 @@ Comprehensive task breakdown for repository improvements and production readines
 ## ✅ Recently Completed
 
 - [x] **Pull Now**: Added "Pull Now" button on Accounts page that immediately queues a `process_mail_account` Celery task via `POST /mail-accounts/{id}/pull-now`. Button shows spinner while in flight and is disabled for inactive accounts.
+- [x] Fixed 21 mypy type errors: `Column[T]` vs native type mismatches in `notification_service.py`, `mail_processor.py`, `auth.py`, `tasks.py`, `providers.py`, `mail_accounts.py`, and `main.py` (`lifespan` parameter rename).
 - [x] **Provider logos rework**: Logos now displayed as full-width banner strips at the top of each account card using `next/image fill + object-contain`. Handles all aspect ratios (1:1 square to 6:1 wordmark) without distortion. Proton Mail added.
 - [x] **Proton Mail provider**: Added Proton Mail preset in backend and ProviderWizard frontend. Domains: proton.me, protonmail.com, protonmail.ch, pm.me. Auto-detect and IMAP/POP3 Bridge settings included.
 - [x] Redesigned user-facing Logs page to mailbox-centric "Mailbox Activity" view: shows last check status per account + only successful pulls, suppressing noise from empty polling cycles.