I've been using Mozilla Thunderbird on Linux for a couple of years now. Naturally, it is one of the first email clients many Linux users look at: open source, powerful, privacy-friendly, and independent from big tech ecosystems.

At first, I struggled a bit with the workflow compared to clients like Microsoft Outlook, especially around searching mails and some UI quirks. Over time, however, I got used to it and now i use for most of my mail tasks (professionally and private).

Yesterday I helped my wife set up Thunderbird on a new windows PC. During that process I noticed several small onboarding and usability issues that imo could and probably will easily discourage new users, especially people who are less technical and are simply looking for a smooth alternative to mainstream mail clients.

I wanted to share this as constructive feedback, but also include the solutions I found in case they help other users experiencing similar issues. Hopefully there are easier options for many "difficulties" we had.

1.Dark mode readability

Dark mode looks ok overall, but replying to emails can sometimes result in black text on a dark background, making messages unreadable.

This can usually be improved via:

Settings → Composition → uncheck “Use reader’s default colors”

However, disabling this also affects how dark mode behaves in the message body. Some views, such as advanced search results, also still seem have readability issues as well with black text on very dark backgrounds.

2.Signature setup feels more technical than expected

Thunderbird supports HTML signatures, which is powerful, but creating and editing them is not very intuitive compared to modern email clients with a built-in WYSIWYG editor.

The workaround I used was:

• create the signature inside a mail
• select the signature
• choose Insert → HTML
• copy the generated HTML
• enable HTML signatures in the account settings
• paste the HTML there

It works, but it is not an easy find for average users.

Than there was an automatic “--” separator added above signatures. This can be disabled via:

Settings → General → Config Editor
search for:

mail.identity.default.suppress_signature_separator

and set it to:
true.

Than, when replying to mails, the cursor always appeared under the signature. This can be changed via:

Account Settings → Composition & Addressing →
“When quoting, start my reply above the quote”

A bit weird that the default setting is to add text under the signature.

And finally there is no possibility it seems to add a signature afterwards to an email automatically with an "insert signature" function. There are add-ons for that, but than you seem to have to create the signature in a second place which does not give a polished impression and is dangerous for forgetting to update one of your signature versions.

3. Attachments are easy to miss

Attachments being displayed below the email body makes them surprisingly easy to overlook.

There is currently no simple built-in option to move them higher in the interface, but I managed to improve this with a custom CSS workaround found on reddit.

Steps:

• create a folder called: chrome inside the Thunderbird profile folder
• create a file called: userChrome.css
• add:

​

#attachmentView, #attachmentBar {
  order: -1 !important;
  background-color: blue !important;
}

Then enable custom stylesheets via:

Settings → General → Config Editor

search for:

toolkit.legacy.userProfileCustomizations.stylesheets

and set it to:
true

After restarting Thunderbird, attachments become much more visible. You can change blue in another color your prefer.

This works well, but it is definitely not something less technical users would easily discover and a bit weird that the user does not get the possibility to alter this location without having to customize css files (as under the body is not the most traditional location).

4. Sending mails feels slower than necessary

There is no incline mail editor like for example outlook which allows to reply on mails without opening a new tab or window but this is just getting used to i think.

However, when sending an email, Thunderbird shows a sending progress dialog for a few seconds. This quickly becomes very annoying when you want to reply or forward multiple emails quickly.

I later discovered this can be disabled via:

Settings → General → Config Editor

search for:

mailnews.show_send_progress

and set it to:
false

After that, sending happens smoothly in the background, which feels much more modern. But it makes you wonder why this is not a default setting?

6. Default email formatting

By default, pressing Enter creates paragraph spacing instead of a simple new line.

This can be changed via:

Settings → General → HTML Style

and unchecking:

“Use paragraph format instead of body text by default”

Again, easy once you know it exists, but probably confusing for first-time users.

7. Exchange / shared mailbox experience

Using Exchange through Owl for Exchange works reasonably well, but shared mailboxes can become visually cluttered.

Folders from shared mailboxes tend to blend into the main mailbox tree rather than clearly appearing as separate accounts like they do in most other email clients. For users managing multiple shared mailboxes, this can become confusing and messy quickly.

I also could not find an easy way to unsubscribe from certain shared folders like you often can with IMAP accounts.

Marking frequently used folders as Favorites however does help significantly.