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<form> in Thunderbird

Works <form> works in Thunderbird.

Works in 10 of 21 · partial in 4 · not supported in 7

Which clients
Works
Gmail, Gmail Android, Outlook iOS, Outlook Android, Apple Mail, Apple Mail iOS, Yahoo Mail Android, Samsung Mail, Thunderbird, AOL Mail
Partial
Gmail iOS, Outlook 365, Outlook (New), Outlook for Mac
Not supported
Outlook Classic, Yahoo Mail, Yahoo Mail iOS, HEY Mail, Proton Mail, Fastmail, Superhuman

The fix for the clients that need it

Needed in 11 of 21: Outlook Classic, Yahoo Mail, Yahoo Mail iOS and 8 more.

Replace embedded form with a link to a hosted form

instead 
<table role="presentation" cellpadding="0" cellspacing="0">
  <tr>
    <td style="background-color: #6d28d9; border-radius: 6px;
               padding: 12px 32px;">
      <a href="https://example.com/subscribe"
        style="color: #fff; text-decoration: none;
               font-family: Arial, sans-serif;
               font-weight: bold;">
        Subscribe Now
      </a>
    </td>
  </tr>
</table>
Show the original
before 
<form action="/subscribe" method="POST">
  <input type="email" placeholder="Email" />
  <button type="submit">Subscribe</button>
</form>

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Your next question

Every feature in Thunderbird · <form> in every client

Questions

How many email clients support <form>?
It works in 10 of 21, partial in 4, not supported in 7.
Does <form> work in Apple Mail?
<form> works in Apple Mail. Closest to Thunderbird: Apple Mail, which agrees on 219 of the 261 features both are tested on.

To see what in your email Thunderbird does not support, paste the whole email.

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caniemail (MIT) via @emailens/engine 0.18.22 · tested upstream 10 Sep 2019 · data last changed 10 Nov 2026 · Outlook (New) cells are the engine's mapping