Outlook Is Not Sending or Receiving Email
Outlook Is Not Sending or Receiving Email
Use this checklist when messages stay in the Outbox, new mail does not appear, or recipients report that your mail never arrived. Work from the least disruptive checks downward. Do not delete your Outlook profile, mail data files, or account until support has confirmed that your mailbox data is safe.
1. Determine the scope
Open Outlook on the web and sign in with the affected work account. Send a short test message to yourself, without an attachment.
- If web mail also fails, the issue may involve the account, mailbox quota, service, or message itself.
- If web mail works but the desktop app does not, focus on the app's connection, sync state, or profile.
- If only one recipient or sender is affected, capture the address, time, subject, and any non-delivery report. Do not resend the same message repeatedly.
Confirm that other websites load. In classic Outlook, look at the status bar. Disconnected, Working Offline, or Trying to connect means Outlook cannot currently reach the mail service. Select Send/Receive > Work Offline once to return online, then choose Send/Receive. In new Outlook, use View > Sync to request a manual sync when that option is available.
2. Check the Outbox and attachment size
Open Outbox and start with the oldest stuck message. A large or damaged message can block later mail. If it has a large attachment, remove the attachment and send a OneDrive or SharePoint link instead, or send a smaller file. Microsoft notes that some providers reject messages over their size limit; the exact limit can vary.
If the message is open or Outlook keeps trying to send it, switch to offline mode briefly, move the item to Drafts, then return online and recreate it. Preserve any important text before deleting a stuck draft. For a non-delivery report, read the error carefully; it may identify an invalid address, blocked file type, size limit, or full destination mailbox.
3. Check storage, password, and folders
A mailbox over quota may be unable to send or receive. In new Outlook choose Settings > Accounts > Storage; in Outlook on the web choose Settings > Account > Storage. Emptying Deleted Items and Junk Email can help because those folders count toward mailbox storage.
If you recently changed the account password, complete the Outlook sign-in prompt with the new password. First confirm the new password at Microsoft 365 in a browser. Never approve an unexpected MFA request or share a verification code.
For missing incoming mail, check Junk Email, Deleted Items, Archive, and focused/other inbox views. Review your own inbox rules for unexpected moves or forwarding, but do not change organization-wide mail-flow or security settings. Search for the sender and subject across all folders.
4. Restart and test safely
Close Outlook, restart the device, install available Office/Outlook updates, and test again. Classic Outlook users can use Microsoft's supported troubleshooters from the official Outlook troubleshooting page. If support asks you to test safe mode, press the Windows key, enter outlook.exe /safe, and test a simple message. If mail works only in safe mode, report that result; do not randomly remove business add-ins.
Office repair or a new profile may be appropriate later, but both should follow a backup/data-location check and help-desk guidance. A POP mailbox or local PST can contain data not stored in Microsoft 365.
When to escalate
Contact your IT help desk when web mail also fails, several users are affected, the mailbox is licensed incorrectly, a non-delivery report mentions policy or transport rules, security software blocks mail, or the problem continues after the checks above.
Provide: sender and recipient addresses, exact time and time zone, subject, whether web mail works, Outlook version, connection status, attachment size/type, and the complete non-delivery report. Do not forward confidential message contents unless requested through an approved support channel.