Mozilla Thunderbird email setup
Configure Thunderbird with secure UKC IMAP and SMTP settings
Use Manual configuration when automatic discovery does not find the correct values. Choose IMAP port 993 with SSL/TLS and SMTP port 587 with STARTTLS, with Normal password authentication and the full email address as both usernames.
Before opening Account Setup
Confirm the address
The address must exist as a mailbox, not only as an email forwarder.
Test webmail
Confirm the full email address and password can sign in and send mail.
Copy the server name
Open Plesk Mail Client Setup and use the exact supported hostname.
Install current Thunderbird
Update the application before troubleshooting a setup screen that differs from this guide.
Thunderbird IMAP and SMTP settings
| Thunderbird field | Incoming | Outgoing |
|---|---|---|
| Protocol | IMAP | SMTP |
| Hostname | Exact hostname shown in Plesk | Exact hostname shown in Plesk |
| Port | 993 | 587 |
| Connection security | SSL/TLS | STARTTLS |
| Authentication method | Normal password | Normal password |
| Username | Complete email address | Complete email address |
Use SMTP port 465 with SSL/TLS only when implicit TLS is needed. If you deliberately require POP3, choose port 995 with SSL/TLS. IMAP is recommended for synchronisation with phones, other computers and webmail.
Add the mailbox to Thunderbird
Open Account Settings, choose Account Actions and Add Mail Account. A first launch may open this form automatically.
Enter the sender name, complete email address and mailbox password, then continue.
Replace any guessed values with the exact incoming and outgoing settings above. Check both usernames.
Use Re-test, then Done. Send to another address, reply and confirm both directions work.
Check an existing Thunderbird account
Open Account Settings and select Server Settings under the mailbox to check the IMAP hostname, port, connection security, authentication method and username. Then select Outgoing Server (SMTP), edit the server used by this identity and verify its hostname, port, STARTTLS, Normal password and full username.
If several accounts are configured, also confirm that the mailbox identity is assigned to the correct SMTP server. A correct server with the wrong saved identity can still reject sending.
Thunderbird troubleshooting
Configuration could not be verified
Open Manual config and check every value. Automatic discovery may not know the exact hostname assigned to the UKC mailbox.
Sending fails but receiving works
Edit Outgoing Server (SMTP). Confirm port 587, STARTTLS, Normal password and the complete email-address username.
Password is rejected repeatedly
Test webmail, then remove the saved password for the affected hostname from Thunderbird’s Passwords settings and enter the current password again.
Certificate warning appears
Do not add a permanent exception for an unexpected certificate. Correct the hostname so it matches the supported service certificate.
If the fault also appears in webmail, follow the email sending and receiving diagnostic guide.
Thunderbird setup questions
Should Authentication method be OAuth2?
Use Normal password for a standard UKC Plesk-hosted mailbox. OAuth2 is appropriate only when the actual mailbox provider supports and requires it.
Why does Thunderbird show two usernames?
Incoming IMAP and outgoing SMTP are separate services. Enter the complete email address for both.
Can Thunderbird import an old local mail archive?
That is separate from adding the live mailbox. Back up the Thunderbird profile and old messages before migrating or removing an existing POP account.
Can I switch an existing POP account to IMAP?
Create and test a separate IMAP account first, then move or copy mail carefully. Do not remove the POP account until any locally stored messages are backed up.
Client workflow reference: Mozilla’s current Thunderbird getting-started guide and account configuration reference. Server-setting reference: Plesk Mail Client Setup documentation.
Still unable to connect?
Send the settings and error, never the password
Include the Thunderbird version, operating system, whether webmail works and the exact incoming or outgoing error.