Gmail won’t send when storage is full, limits are hit, attachments are blocked, or sync/auth breaks—use the checks below.
Quick Answer And First Steps
You’re looking at a stuck Outbox or a spinning send icon. The fastest path is to rule out the usual culprits in a set order. Start with connection, storage, and attachment size, then move to account limits and app settings. The table below gives a speedy triage you can run in minutes.
| Symptom | Likely Cause | Fast Fix |
|---|---|---|
| Message stuck in Outbox | No data or flaky Wi-Fi | Toggle Airplane Mode off/on and resend |
| Attachment never finishes | Over 25 MB total | Send via Drive link or compress the file |
| Instant bounce or “You have reached a limit” | Daily send cap or rate limit | Wait, reduce recipients, or send later |
| “Storage full” banner | Google storage at capacity | Free space or buy storage |
| Works on web, not in app | Sync/auth issue in client | Re-login; clear cache; update the app |
| “Blocked for security reasons” | Prohibited file type | Share via Drive or zip/rename safely |
Common Reasons Mail Stays In Outbox
Storage Is At Capacity
Google storage is shared across Mail, Drive, and Photos. When it’s full, sending stops. Clear large mail threads and trash, empty spam, and delete heavy Drive items you no longer need. If space is tight every week, a small Google One plan saves time and keeps sending smooth.
Attachments Are Too Large Or Blocked
Mail attachments top out at 25 MB across all files on one message. Large files switch to a Drive link. Some file types are never allowed for safety, even inside a zip. If you hit either wall, share from Drive with view access or use a safer archive.
Send Caps Or Rate Limits
Mail has daily caps and recipient limits to curb spam. Mass sends, big BCC lists, or repeated retries can trigger a temporary block. Space sends across time, prune big lists, and keep test blasts small. If you run a newsletter, use a proper sender platform.
Offline Mode Or Patchy Connection
On phones and laptops, a poor link leaves messages queued. Flip Wi-Fi off and on, try mobile data, or move to a stronger signal. On the web, turn off Offline mode until the queue clears.
App Cache, Sync, Or Profile Glitches
A stale token or bug can break send on one device while the web works. Sign out and back in, update the app, and clear cache. On Android, also check “Sync Gmail” under account settings. On iPhone, remove and add the account again to refresh OAuth.
Service Disruption
On rare days, a service hiccup affects sending worldwide. If the inbox loads but send fails on every device, check the status site and try again later.
Gmail Not Sending Messages? Real-World Fix Order
Work through the list in this order for a fast win. It tackles the highest-odds fixes first and avoids chasing edge cases.
- Check connection. Send a short plain-text message to yourself on mobile data, then on Wi-Fi.
- Review storage. Open the account storage page and free space until you’re under quota.
- Trim the attachment. Keep the total under 25 MB or send a Drive link with the right share right.
- Retry with fewer recipients. Remove big BCC lists or batch in smaller groups.
- Turn Off Offline. In web settings, disable Offline until the Outbox is clear.
- Re-auth the app. Sign out/in; clear cache; update. Then resend the stuck draft.
- Check status. If nothing moves on any device, confirm service health and wait out a live incident.
Storage Fixes That Free Sending
Target the biggest wins: search for “larger:10m”, delete old video threads, empty Trash and Spam, and clear giant Drive folders. Photos in Original quality chew space; switch to Storage saver for future uploads. Keep an eye on the storage meter so send never stalls mid-day.
Attachment Rules And Safer Workarounds
Heavy files and risky formats stop a send cold. Use the guide below to stay inside the guardrails and still get the file across.
| Item | Limit/Rule | Workaround |
|---|---|---|
| Total attachment size | Up to 25 MB per message | Upload to Drive; share link with view access |
| Executable content | Blocked even inside archives | Share from Drive; remove executable parts |
| Huge media | Slow to upload; may time out | Compress video/photo; send Drive link |
When You Send From Outlook, Apple Mail, Or Other Apps
If sending fails only in a desktop or mobile client, the issue is usually settings, auth, or a stale profile. Start by switching that app to OAuth if it supports it. If you must use a password with two-step verification on, create an app password. Confirm the server names, ports, and TLS, then test with a short plain-text note.
Correct Server Basics
IMAP server is imap.gmail.com on port 993 with SSL/TLS. SMTP server is smtp.gmail.com on port 465 with SSL or 587 with STARTTLS. Username is the full account address. Auth must be on. These defaults work across modern clients.
POP And “Recent Mode”
If you’re on POP, use Recent mode so multiple devices still receive new mail. Turn off the option that deletes mail from the server after download, or it will vanish on the other devices.
Rebuild The Local Profile
When a profile goes bad, send stalls. Create a new profile, add the account fresh, and try again. If that clears it, move mail over and retire the old profile.
Fix Bounces And “Message Rejected” Notices
A bounce means a server refused the message. Common causes: a bad address, a full recipient inbox, an attachment or link that trips filters, or too many sends in a short burst. Check the bounce text for a code and message. Small edits help: shorten subject lines, remove huge images, and link to files instead of attaching.
Custom Domain Senders
If you send as you@yourdomain.com through Google, add SPF and DKIM at your DNS host so recipient servers trust your mail. That’s outside most personal setups, but it fixes many “550” style rejects for domain senders.
Prevent Sending Problems Next Time
- Keep storage below the cap by clearing large threads monthly.
- Use Drive links for anything bigger than a few megabytes.
- Send to smaller groups and avoid repeated retries.
- Update the mobile app and desktop client each month.
- Use OAuth where possible; rotate app passwords if required.
- Skip risky file types; share them from Drive instead.
Need A Quick Link Or Two While You Fix?
You can check recipient and daily caps on the official sending limits page, and see which file types are blocked before you try again. Keep both handy when you run into a stubborn Outbox.
Android And iPhone Fixes That Work
Refresh The Account Token
Open the mail app, remove the account, then add it again. This forces a clean OAuth handshake and clears stale tokens that can stop outbound mail while everything else looks normal.
Clear Cache And Storage (Android)
In Settings › Apps › Gmail, tap Storage. Clear cache first; if send still fails, clear storage to reset the app. You won’t lose mail on the server, and a fresh sync often frees stuck drafts.
Check Background Data
Make sure background data and battery settings aren’t restricting the app. If battery saver blocks network calls, sends sit in the queue until you open the app or plug in the phone.
Speedy Fixes On The Web
Turn Off Offline
In Settings › See all settings › Offline, disable it until everything sends. Offline mode helps on planes, but a partial sync can leave drafts stranded.
Try A Clean Browser Session
Open a private window or another browser and send a short test message. If it works there, the issue is a cookie, extension, or profile. Disable extensions that rewrite pages, block scripts, or scan content.
Check Filters And Forwarding
A filter that forwards or deletes based on a pattern can collide with send rules. Review active filters and any forwarding maps that touch outbound mail.
Account Security And Admin Rules
Unusual sign-in alerts, password changes, or a device flood can trigger extra checks. If you see repeated prompts, finish two-step verification on all devices and review trusted devices. School or work accounts may also cap recipients, block auto-forward, or restrict specific file types. If personal mail sends fine but your work account stalls, ask the admin if a rule changed.
What To Do When Nothing Works
Try the web first. If the web sends, the device is the problem; rebuild that app profile. If the web won’t send either, bring storage under quota, strip the attachment, and retry with a one-line note to a single address. If you still get a bounce or rate message, wait an hour and send again. During a live status incident, sending may return on its own once service stabilizes.