Message Composition

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Send Later

True "Send Later" functionality to schedule the time for sending an email.

Rated 5 out of 5 stars (269)
114,713 users

Grammar and Spell Checker — LanguageTool

Check your emails for spelling and grammar issues

Rated 4 out of 5 stars (50)
73,381 users

Mail Merge

Create and Save or Send Multiple Individual and Personalized Messages from a Draft

Rated 5 out of 5 stars (237)
73,044 users

Signature Switch

Switch the signature on/off or choose a new one from your predefined set.

Rated 4 out of 5 stars (311)
53,035 users

FileLink provider for Send

Securely encrypt and upload large attachments to any Send service instance (formerly Firefox Send).

Rated 5 out of 5 stars (17)
51,699 users

FileLink Provider for Dropbox

Uploads your large attachments to your Dropbox instead of sending them by email. This uses Thunderbird's FileLink feature.

Rated 4 out of 5 stars (25)
50,087 users

Textmarker

Highlights selected text when composing emails. Default colour is yellow - other colours are available via Options.
(Works only during writing an e-mail, i.e. only in the compose window.)

Rated 5 out of 5 stars (38)
47,583 users

Owl for Exchange

Allows you to use your Exchange and Office365 email account with Thunderbird using Outlook Web Access (OWA).

Rated 5 out of 5 stars (227)
44,038 users

*cloud - FileLink for Nextcloud and ownCloud Featured

Upload large attachments to your Cloud and send the link by email

Rated 5 out of 5 stars (56)
39,096 users

Emoji

Add emojis to your e-mails.

Rated 4 out of 5 stars (66)
24,099 users

FlexConfirmMail Stable

Confirm mail address and attachments based on flexible rules.

This is enterprise edition with less updates. Another edition for regular users:
https://addons.thunderbird.net/thunderbird/addon/flex-confirm-mail/

Rated 4 out of 5 stars (11)
23,034 users

Check and Send

Check the message contents and addresses before you send the message...

Rated 4 out of 5 stars (51)
20,219 users

FileLink Provider for Box

Uploads your large attachments to your Box instead of sending them by email.

Rated 3 out of 5 stars (14)
11,264 users

ReplyWithHeader

Outlook style headers and few goodies for Thunderbird.

Rated 4 out of 5 stars (100)
10,714 users

Simple Mail Redirection

Allows you to resend (also known as redirect) email messages.
Uses 'cardbook' if installed

Bases on the add-on 'Mail Redirect' by Onno Ekker and Pawel Krzesniak

Please see the support page on how to use and why it sometimes does not work!

Rated 5 out of 5 stars (39)
8,969 users

ThunderAI (ChatGPT, Gemini, Ollama in your emails)

ThunderAI uses the capabilities of ChatGPT, Google Gemini, Claude or Ollama to enhance email management.
It enables users to analyze, write, correct, assign tags, create calendar events and tasks and optimize their emails.

Rated 5 out of 5 stars (22)
8,131 users

BorderColors D

Shows a colorful border around the "New Message" window, so you can tell different identities apart.

Builds on the original BorderColors and the "GT" version, adding different border styles.

Rated 4 out of 5 stars (36)
7,956 users

CategoryManager

Category manager for Thunderbird contacts, also allows to send an email to all members of a category (categories can be used as contact groups).

Rated 5 out of 5 stars (26)
6,222 users

Identity Chooser

Identity Chooser helps you to always use the correct identity when composing a new email.

Rated 4 out of 5 stars (149)
6,083 users

Emoji

It permits just with a single click to copy an emoji.
There is a search-box and the "Most used emojis" section (the first one).

If you want to send feedback or report bug, please contact me

Rated 5 out of 5 stars (16)
5,931 users