First send one message from Roundcube
If Roundcube sends successfully, the mailbox and UKC outgoing service are working. Concentrate on the mail application's SMTP settings or the local network. If Roundcube also fails, keep its exact error.
Recommended outgoing settings
Use authenticated and encrypted SMTP
- SMTP server
- Your assigned UKC server, for example ukc12.uk
- Username
- Your complete mailbox email address
- Password
- Your mailbox password
- Authentication
- Required
- Preferred
- Port 465 with SSL / TLS
- Alternative
- Port 587 with STARTTLS
Do not use a raw IP address or `mail.your-domain` when the assigned UKC hostname is available. The server hostname matches the mail certificate and avoids identity warnings.
Network comparison
Test whether the connection is being blocked locally
- Confirm the application uses port 465 or 587, not port 25.
- Temporarily test from another trusted network, such as a mobile hotspot.
- If sending works there, review the original router, firewall, antivirus email scanning or internet-provider restrictions.
- Restore normal protection after the comparison; do not leave security software disabled.
Read the exact error
Common outcomes
- Authentication failed
- Check the full email address and password, then reset the mailbox password if needed.
- Timeout or refused
- Check the hostname, port, encryption and local network.
- Certificate warning
- Use the assigned UKC server hostname.
- Spam or sender restriction
- Stop retries and follow the BadMailFrom or bounce guidance shown by the error.
- Recipient rejected
- Test another destination and retain the complete remote rejection.
A Spamhaus message may identify the connecting network
Do not assume every listed IP belongs to the UKC mail server. Keep the complete error and identify whether it names your home or office public IP, the UKC server, or a remote relay before requesting delisting.
Sending still fails?
Include the mailbox address, mail application, assigned UKC server, port, encryption, date and time, whether Roundcube worked, whether another network worked, and the complete error. Never send the mailbox password.
Ask the Email team