When email stops arriving, the cause is usually one of a few things: the message went to another folder, a filter or forwarding rule is intercepting it, your mailbox is full, your app has stopped syncing, or the sender's message was rejected. This guide helps you work out which one applies and fix it without changing settings you don't need to touch.
Start by narrowing down the problem
Three quick questions point you to the right section:
- Is it missing from webmail too? Sign in through your provider's website (for example, gmail.com or outlook.com). If the message appears there but not in your phone or desktop app, the problem is app syncing. If it's missing everywhere, the problem is on the account or delivery side.
- Is it everyone or specific senders? Missing mail from one sender suggests a filter, block, or problem on their end. Missing mail from everyone suggests storage, account, or server issues.
- Did the sender get an error? A bounce-back message (often titled "Undeliverable" or "Delivery Status Notification") usually states the reason. Ask them to send it to you.
Fixes to try first
1. Check spam, junk, and sorted tabs
Look in Spam or Junk first. Then check the other places mail can land:
- Gmail: the Promotions, Social, and Updates tabs, plus Trash and All Mail.
- Outlook: the Other tab if Focused Inbox is on, plus Junk Email and Deleted Items.
Search for the sender's address or a distinctive subject word across all folders. If you find the message in spam, mark it as "Not spam" (Gmail) or "Not junk" (Outlook) and add the sender to your contacts or safe senders list.
2. Check your storage
A full mailbox can cause incoming mail to be rejected or delayed. Senders often receive a "mailbox full" error. On Google accounts, storage is shared across Gmail, Google Drive, and Google Photos, so large files elsewhere can fill it. Microsoft and other providers have their own mailbox limits.
Check your usage in your account's storage page, then delete large attachments, empty Trash and Spam, or buy more storage. Because deleting is permanent once Trash is emptied, review what you're removing first.
3. Look for filters, rules, and forwarding
A forgotten rule can archive, delete, or redirect mail before you see it.
- Gmail (on a computer): click the gear icon, choose See all settings, then check the Filters and Blocked Addresses tab and the Forwarding and POP/IMAP tab.
- Outlook.com: open Settings, then Mail, and review Rules, Junk email (blocked senders), and Forwarding.
- Other providers: look in webmail settings for similar sections. Names vary.
Delete or edit any filter that deletes, skips the inbox, or forwards mail you didn't set up. Also check the blocked senders list for the person you're expecting.
If you find a forwarding address or rule you didn't create, treat it as a possible account compromise. Change your password right away, turn on two-step verification, and review recent sign-in activity in your account's security page.
4. Send a test message
Send an email to yourself, then have someone (or another account you own, on a different provider) send one to you.
- Self-sent mail arrives, outside mail doesn't: the issue is likely filtering, blocking, or delivery from external senders.
- Nothing arrives, even from yourself: suspect storage, a sync problem, or an account or server issue.
If webmail works but your app doesn't
This is a sync problem, not a delivery problem. Work through these in order:
- Confirm the device is online and try opening the app's refresh or sync option.
- Check that the app is signed in. A recent password change, expired sign-in, or security prompt can silently pause syncing. If the app asks you to sign in again, do so.
- Look at the account's sync settings in the app. Make sure email sync is on and the "days of mail to sync" setting isn't limiting what you see. On phones, also check that background data or battery restrictions aren't blocking the app.
- Update the app and your device's operating system.
- As a last step, remove the account from the app and add it again. For IMAP and Exchange-style accounts, mail stays on the server, so this is generally safe. For POP accounts, mail may be stored only on that device, so back it up or confirm it's also on the server first.
If you use more than one device, check whether any is using POP. POP can download messages and, depending on its settings, remove them from the server, so another device may seem to "steal" your mail. IMAP keeps devices in sync and is usually the better choice for multiple devices. Your provider's help pages list the correct incoming server settings.
Reading bounce messages
If a sender gives you the error text, the code can help:
- 5.1.1 or "user unknown": the address is wrong or doesn't exist. Check for typos, or confirm the account is still active.
- 5.2.2 or "mailbox full": free up storage as described above.
- 4.x.x codes: temporary failures. The sending server usually retries for a while, so delays may resolve themselves.
- 5.7.x or "rejected" / "blocked" / "policy": the message was refused for security or spam reasons. This can come from your provider, the sender's provider, or authentication problems on the sender's domain. The sender or their email administrator may need to fix it.
Exact wording differs by provider, so rely on the text in the message rather than the code alone.
If you use a custom domain (name@yourbusiness.com)
When no mail arrives at a domain-based address, the usual suspects are an expired domain, changed hosting, or incorrect MX records. MX records are DNS settings that tell the internet which service receives mail for your domain.
- Confirm the domain registration hasn't expired.
- Look up your domain's MX records with a free tool such as Google's Admin Toolbox Check MX or MXToolbox.
- Compare the results with what your email provider (Google Workspace, Microsoft 365, or your host) says they should be. Their setup documentation lists the correct values.
Before editing DNS, copy down or screenshot the existing records. A wrong change can stop all mail to the domain. If you aren't comfortable with DNS, ask your host or email provider's support team.
Outages and delays
If everything looks correct, check your provider's service status page (for example, the Google Workspace Status Dashboard or Microsoft's service health page). Large outages are rare, but delays during them can last from minutes to hours. Don't change settings during an outage unless the provider tells you to.
How to confirm it's fixed
- A test email from another provider arrives in your inbox within a few minutes.
- The same message appears in both webmail and your app.
- The person who had trouble sending can send again without a bounce-back.
- Sending a reply still works, so you know you didn't break outgoing mail.
When to contact support
If the basics check out and mail is still missing, contact your email provider or, for a custom domain, your host or IT administrator. Give them the sender's address, the approximate time of the failed message, and the full bounce text if there is one. Those details let them trace the message instead of guessing. If you suspect your account was accessed by someone else, secure it first by changing your password and reviewing sign-in activity, then contact support.