---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/sendgrid/for-developers/sending-email/thunderbird#article
headline: Thunderbird
description: Learn to modify Thunderbird's outgoing server settings and send emails with an SMTP API header. Step-by-step guide for efficient mail management.
url: https://www.twilio.com/docs/sendgrid/for-developers/sending-email/thunderbird
inLanguage: en
dateModified: 2026-07-23T16:57:51.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# Thunderbird

To send email using Thunderbird you will have to modify your outgoing server settings in Thunderbird accordingly. Additionally you can modify settings in Thunderbird that will allow you to include an [SMTP API](/docs/sendgrid/for-developers/sending-email/building-an-x-smtpapi-header) header in your emails if you wish to leverage [categories](/docs/sendgrid/ui/analytics-and-reporting/categories/) or other features of the SMTP API when sending mail via the Thunderbird client.

## Configure your outgoing server settings

To configure Thunderbird to send email through Twilio SendGrid, follow these steps:

1. Navigate to **Tools** and select **Account Settings**.

![Thunderbird SMTP settings with SendGrid server highlighted and add button indicated.](https://docs-resources.prod.twilio.com/3ab8d03cc08a768af5ea15aa1eebb2af9d6aef18c836862865b147186528421b.png)

2. Enter the following settings:

   * **Description -** SendGrid Connection
   * **Server Name -** smtp.sendgrid.net
   * **Port -** 465
   * **Connection security -** SSL/TLS
   * **Authentication method -** Normal password
   * **User Name -** apikey
   * **Password -** Your SendGrid API key. (You can read more about authenticating with an API key at [this link](/docs/sendgrid/for-developers/sending-email/upgrade-your-authentication-method-to-api-keys/#upgrade-to-api-keys-for-your-smtp-integration))

![SendGrid SMTP settings with server name, port, and authentication details.](https://docs-resources.prod.twilio.com/3b03125a00f636148077e29eb3b6d89de65de14eaa2b676d21edf207b7045515.png)

## Incorporating SMTP API headers

*To incorporate SMTP API headers:*

1. Select **Tools** > **Options** (Win) or **Thunderbird** > **Preferences** (Mac) from the menu in Thunderbird.
2. Click **Advanced**.
3. Select **General** and click **Config Editor**.

![Thunderbird Advanced settings with Config Editor button highlighted.](https://docs-resources.prod.twilio.com/caa1071e6d584a5ba32614d4f651dd7aac98c7a86c84038b3117bffd0668a54c.png)

4. Enter "mail.compose.other.header" under "Filter:"
5. Double-click **mail.compose.other.header**.
6. Enter "X-SMTPAPI"
7. Click **OK**.
8. Close the configuration editor and preferences dialog.

![Thunderbird config showing mail.compose.other.header set to X-SMTPAPI.](https://docs-resources.prod.twilio.com/3e29e1ca05faaca46afbe752944f00e915deb18c169a7d2ab5860dc11c092751.png)

9. Restart Thunderbird

Create a mail message and just like you would add a CC or BCC to your email, click the drop down option that will now allow you to add a header of the type "X-SMTPAPI" in addition to "To".

![Email composition window with X-SMTPAPI field set to category 'Welcome'.](https://docs-resources.prod.twilio.com/067da9109fa9c60eb3fadbace3dcdc54f130fd2b2740ef6a407061da40433ab8.png)