The mail server needs proof that the request is authorised
UKC rejects unauthenticated sending and delivery to addresses that do not exist. This limits spam from compromised websites and prevents the server acting as an open relay.
If outgoing mail fails
Enable SMTP authentication
- SMTP server
- Your assigned UKC server, for example ukc12.uk
- Username
- Your complete mailbox email address
- Password
- The mailbox password
- Authentication
- Required
- Preferred connection
- Port 465 with SSL / TLS
- Alternative
- Port 587 with STARTTLS
In a website or plugin, select authenticated SMTP rather than PHP mail where possible. The From address should be a mailbox or address permitted by the authenticated account.
If receiving or forwarding fails
Confirm the destination exists in Plesk
- Log in to Plesk for the hosting service.
- Open Mail for the affected domain.
- Confirm the complete recipient exists as a mailbox, forwarding address or mail alias.
- If it does not exist, create the intended address and test again.
Creating a similarly named mailbox is not enough; the exact address used by the sender must be configured.
Websites and forms
Check the application, not only the mailbox
- Save the correct SMTP host, port and encryption in the application.
- Retype the mailbox password rather than relying on an old saved value.
- Test with the website plugin's built-in mail test where available.
- Check that security software or a hosting firewall does not block the selected port.
Still receiving DENIED_AUTH_REQUIRED?
Send the full bounce or application error, affected address, sending or receiving direction, and confirmation that the address exists. Remove passwords and API keys before attaching logs.
Request email help