Gmail not delivering incoming mail can be caused by several common issues. Here are the most frequent causes and practical steps to diagnose and fix them. What to check first

• Internet connection: Ensure a stable internet connection. If the connection drops, new messages won’t sync until it's restored. Also verify any VPNs or firewalls that might block Gmail.
• Storage space: Gmail shares storage with Drive and Photos. If the Google account is out of storage, new messages may be blocked. Check storage at the bottom of Gmail or in Google One, and free up space or upgrade if needed.
• Account filters and forwarding: Review any active filters, forwarding rules, or POP/IMAP settings that might be moving or removing incoming mail before it reaches your inbox.
• Spam and Trash: Look in Spam and Trash folders. Legitimate messages can land there due to sender reputation, content, or misconfigured filters.
• Mail organization: Ensure not every message is archived automatically. Check Archive view and labels to confirm where messages are going.

Ongoing issues and setup checks

• Email routing changes: If the account is part of a domain or organization, MX records or domain settings could have changed, causing mail to be delivered elsewhere or rejected.
• Gmail outages: Service disruptions can impact mail delivery. Check Google Workspace Status or Google Apps Status dashboards for current outages.
• App/Device sync: If you’re checking on a mobile app, verify account is synced, and consider re-adding the account or updating the app.

Step-by-step fixes

• Confirm storage:
  • Open Gmail, scroll to the bottom to view storage usage, or visit Google One. Clear space by deleting large emails with attachments or transferring them off Gmail, and consider upgrading storage if needed.
• Review filters and forwarding:
  • In Gmail settings, open Filters and Blocked Addresses to disable or delete rules that may be misrouting mail.
  • Check Forwarding and POP/IMAP settings to ensure mail isn’t being forwarded or downloaded elsewhere.
• Check other folders:
  • Use the search box with has:userlabels, is:unread, is:inbox, or is:spam to locate messages and confirm their location.
• Verify recipients and sender behavior:
  • If only certain senders fail, the issue may be on the sender’s side (spam blocks, DMARC/SPF checks) rather than your account.
• Test delivery:
  • Send a test email from a different account and ask the sender to confirm if they receive a bounce or error message.
• Check for account or domain issues (especially for work accounts):
  • If you manage a domain, verify MX records point to Google servers and that there are no domain-level blocks or quarantine rules.
• Check for outages:
  • Look up the Google Workspace Status Dashboard to see if Gmail is experiencing interruptions.

If none of these steps resolve the issue

• Consider contacting Google Support or your organization’s IT administrator for deeper diagnostics, especially if you use a work or school account with enforced security rules.
• Capture any error messages, bounce codes, or timestamps when testing mail delivery; these details aid troubleshooting.

If you’d like, share a bit more detail:

• Are you using a Gmail app, a web browser, or both?
• Do you see any recent filters, forwarding rules, or storage alerts?
• Is the problem affecting all emails or only messages from specific senders?

I can tailor a more precise checklist once you provide those details.