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 (263)
93,027 users

Mail Merge

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

Rated 5 out of 5 stars (226)
60,123 users

Grammar and Spell Checker — LanguageTool

Check your emails for spelling and grammar issues

Rated 4 out of 5 stars (32)
55,663 users

Signature Switch

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

Rated 4 out of 5 stars (272)
48,042 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 (21)
47,678 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 (197)
42,298 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)
39,360 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 (32)
32,025 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 (47)
29,842 users

Emoji

Add emojis to your e-mails.

Rated 4 out of 5 stars (64)
22,993 users

FlexConfirmMail

Confirm mail address and attachments based on flexible rules.

(This project was renamed from "Flex Confirm Mail" to "FlexConfirmMail", due to a branding reason.)

Rated 4 out of 5 stars (11)
20,433 users

Check and Send

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

Rated 4 out of 5 stars (49)
19,149 users

Shrunked Image Resizer

Make your photos smaller, so they don't take forever to email.

*Shrunked Image Resizer is no longer maintained.*

Rated 4 out of 5 stars (88)
12,547 users

FileLink Provider for Box

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

Rated 3 out of 5 stars (12)
12,216 users

ReplyWithHeader

Outlook style headers and few goodies for Thunderbird.

Rated 4 out of 5 stars (88)
10,555 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 4 out of 5 stars (33)
7,747 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 (33)
7,072 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 (23)
6,981 users

Attach from Clipboard

Create file attachments directly from the system clipboard.

Rated 4 out of 5 stars (27)
5,815 users

Identity Chooser

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

Rated 4 out of 5 stars (147)
5,687 users