Email not sending or receiving? Find where the problem starts.

Email, attachments and cloud files can draw on shared storage allowances. This can include OneDrive or Google Drive, depending on the account.

1. Check whether the mailbox or cloud storage has reached its limit.
2. Remove messages with large attachments that you no longer need.
3. Clear the Deleted Items or Trash folder.
4. Check the storage status in your cloud account.

A full mailbox may refuse incoming mail, leaving the sender with a Mailbox Full error.

For classic Outlook, use this check when webmail works but the app has frozen or stopped synchronising. A message with a large attachment can remain in the Outbox and hold up delivery.

1. Open Outlook and choose Send / Receive > Work Offline to disconnect it.
2. Open Outbox in the folder list on the left.
3. Right-click the queued message and choose Delete. To keep it for editing instead, drag it into Drafts.
4. Choose Work Offline again to reconnect Outlook.
5. Try sending the message again.

New Outlook may have damaged local data. In Windows 11, open Settings > Apps > Installed apps and find Outlook (New). Select its three-dot menu, choose Advanced options, then scroll to Repair and select it.

The repair fixes the app's files while leaving your emails intact.

This applies to manually configured accounts, including custom business addresses and older ISP mailboxes using IMAP, POP3 or SMTP. A wrong port or encryption choice can prevent a connection.

In classic Outlook, open Control Panel > Mail and create a new profile. Follow our steps for creating a new Outlook profile.

Unless the provider specifies otherwise, enter the complete email address as the username. Check the password before testing.

Telstra Mail and BigPond share the Telstra server settings.

• Incoming IMAP: server imap.telstra.com, port 993, encryption SSL. Use the full Telstra email address; authentication is required.
• Outgoing SMTP: server smtp.telstra.com, port 465 with SSL/TLS, or port 587 with STARTTLS. Authentication is required; select Use same settings as my incoming mail server.

These addresses can end in @bigpond.com, @bigpond.net.au or @telstra.com.

OptusNet recommends IMAP over POP3. See the OptusNet email application settings.

• Incoming IMAP: server mail.optusnet.com.au, port 993, encryption SSL/TLS. Authentication is required. Enter the whole email address, such as [email protected].
• Outgoing SMTP: server mail.optusnet.com.au, port 587 with STARTTLS, or port 465 with SSL/TLS. Authentication is required.

Optus still supports port 25, but new mail clients should use 587 or 465.

If you have an iPrimus or AAPT address, check who now hosts your mailbox and use that provider's settings.

If messages arrive but will not send, outgoing SMTP authentication may be switched off.

1. In classic Outlook, open Control Panel > Mail > Email Accounts, select the account, then choose Change > More Settings > Outgoing Server.
2. Find Outgoing Server (SMTP).
3. Tick My outgoing server (SMTP) requires authentication.
4. Choose Use same settings as my incoming mail server.

Third-party products such as Avast, McAfee and Norton can include email scanning. An email-protection feature can sit between the app and the mail server, inspecting incoming and outgoing traffic. Certificate expiry or a conflict with a Windows 11 update may interrupt connections on ports such as 993 or 465.

Do not delete your security software.

1. Open the third-party antivirus program.
2. Turn off its email-scanning feature.
3. Test synchronising or sending mail again.

If mail starts working straight away, the email-scanning feature may be involved.

A VPN can make a sign-in appear to come from another country or an unfamiliar location. Disconnect the VPN, then test synchronising or sending mail.