Set Up Business Email in Thunderbird (IMAP, Manual Configuration)

Thunderbird is the mail app most people reach for when they want one program for several accounts on a laptop, and it is also the simplest to set up by hand: one screen with every field visible, a Re-test button that tells you exactly which setting is wrong, and no cloud in between. The automatic lookup will not find settings for a custom domain, so this guide goes straight to manual configuration and then through the three settings worth changing afterwards.

Quick answer

Account Settings, Account Actions, Add Mail Account. Enter your name, address and webmail password, click Continue, then Configure manually. Incoming: IMAP, hostname mail.oqumail.com, port 993, connection security SSL/TLS, authentication Normal password, username your full address. Outgoing: hostname mail.oqumail.com, port 587, connection security STARTTLS, Normal password, same username. Click Re-test, then Done.

The settings you will enter

• Incoming (IMAP) server: mail.oqumail.com, port 993, SSL/TLS on
• Outgoing (SMTP) server: mail.oqumail.com, port 587, STARTTLS (apps that offer only an SSL switch: on, with port 587)
• Username: your full email address, for both incoming and outgoing
• Password: the same password you use for OquMail webmail

Step by step

1. Open Thunderbird. Click the menu button (three lines) and choose Account Settings, then Account Actions at the bottom left, then Add Mail Account. On a fresh install the same screen opens automatically.
2. Enter your full name as recipients should see it, your full email address and your webmail password. Leave Remember password ticked. Click Continue.
3. Thunderbird searches for settings and reports that it could not find them. Click Configure manually to open the full form.
4. Incoming server: Protocol IMAP, Hostname mail.oqumail.com, Port 993, Connection security SSL/TLS, authentication (proof that email really comes from your company) method Normal password, Username your full email address.
5. Outgoing server: Hostname mail.oqumail.com, Port 587, Connection security STARTTLS, authentication (proof that email really comes from your company) method Normal password, Username your full email address.
6. Click Re-test. Both lines should turn green with "The following settings were found by probing the given server". If one stays red, the error names the server and the setting to change.
7. Click Done. Thunderbird fetches the folder list and begins syncing the inbox.
8. Send a test message to another address you own and reply to it from there.

Three settings worth changing

• Account Settings, your account, Server Settings: Check for new messages every 10 minutes is the default; IMAP IDLE (Allow immediate server notifications) keeps the inbox live. Leave Empty Trash on Exit off unless you want deletions to be permanent.
• Synchronization & Storage: Keep messages for this account on this computer is on by default. On a laptop with a small disk, set Synchronize the most recent 90 days and leave older mail on the server, where it stays searchable.
• Copies & Folders: confirm Sent, Drafts and Archives point at the folders on the server (under your account name), not Local Folders, so webmail and your phone see what you sent.

If something goes wrong

• "Username or password invalid" on Re-test: the username must be the full address and the password is the webmail one. Test it in webmail first.
• Incoming green, outgoing red with "server does not support STARTTLS": the outgoing port is 465 or the security is SSL/TLS. Port 587 with STARTTLS is the pair; see STARTTLS errors.
• "Add Security Exception" dialog: the hostname is not mail.oqumail.com. Cancel and correct it rather than adding an exception.
• Sent messages not in webmail: Copies & Folders is pointing Sent at Local Folders.
• Folders missing: right-click the account, Subscribe, and tick the folders you want to see.

Common questions

Does this work on Linux?

Yes. Thunderbird is the same program on Windows, macOS and Linux, and the settings are identical.

Can I use Thunderbird to back up the mailbox?

Yes. With the account synced, Local Folders is a complete offline copy, and you can export it; the backup guide explains how.

Thunderbird on Android?

Thunderbird for Android (the former K-9 Mail) uses the same settings: IMAP mail.oqumail.com port 993 SSL/TLS, SMTP mail.oqumail.com port 587 STARTTLS, full address as username.