Sender Domain Column for Thunderbird

Adds a Sender Domain column to Thunderbird's message list showing the apex domain of each sender's email address — subdomains are automatically collapsed.

Sender address	Column shows
info@abc.com	abc.com
admin@help.xyz.com	xyz.com
noreply@mail.bbc.co.uk	bbc.co.uk

Why this is useful

Thunderbird's default view shows whatever name the sender chose to display — which tells you nothing about where the email actually came from. The Sender Domain column cuts through that and shows the real origin domain at a glance.

Spot spam and phishing faster

Spam and phishing emails often arrive with legitimate-looking display names ("PayPal Support", "Your Bank") but the domain tells the real story. A glance at the Sender Domain column immediately flags anything that doesn't come from the domain you'd expect. You don't need to open the email or hover over anything — the domain is right there in the list.

Sort and group by sender domain

Click the Sender Domain column header to sort your inbox by domain. This clusters all emails from the same organisation together regardless of which address or subdomain they used — billing@, noreply@, support@ all roll up to the same domain. Great for:

• Reviewing everything from a vendor before a meeting
• Seeing how much mail you get from a particular company
• Batch-selecting and filing messages by sender

Manage mailing lists and newsletters

Marketing emails and newsletters often come from sending platforms (mailchimp.com, sendgrid.net, klaviyo.com) rather than the brand's own domain. Sorting by Sender Domain makes it easy to find all your newsletter mail in one sweep, even when the display names are all different.

Audit unfamiliar senders

When clearing a backlog or reviewing an unfamiliar account, sorting by domain gives you a structured view of who has been sending mail — much faster than reading individual From addresses one by one.

Filter and search more precisely

Once you know the domain you care about, Thunderbird's search and filter tools become more powerful. Sort by Sender Domain, select a block of messages, and apply a label, move them, or delete them in bulk.

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Requirements

• Thunderbird 115 or newer

Installation

1. Download sender-domain-column.xpi from the Releases page (or build it yourself — see below).
2. In Thunderbird, open the menu and go to Add-ons and Themes.
3. Click the gear icon ⚙ and choose Install Add-on From File.
4. Select the .xpi file and click Add.

Enabling the column

After installing, the column is hidden by default. To show it:

1. Right-click anywhere on the column header bar in your message list.
2. Tick Sender Domain in the menu.

You can drag it to reorder it and click the header to sort by domain.

Building from source

Requires Windows with PowerShell (no extra tools needed).

git clone https://github.com/jazztunes/Sender-Domain-Column-for-Thunderbird
cd Sender-Domain-Column-for-Thunderbird
build.bat

This produces sender-domain-column.xpi in the project root, which you can install as described above.

How subdomain collapsing works

The extension keeps only the apex domain — the registered part of the hostname:

• Simple domains (abc.com, example.org) are kept as-is.
• Subdomains (mail., help., cdn.) are stripped.
• Country-code second-level domains (co.uk, com.au, gov.uk, etc.) are detected and preserved with their parent label, so mail.bbc.co.uk becomes bbc.co.uk rather than co.uk.

License

MIT