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word-break in Fastmail

Works word-break works in Fastmail.

Works in 4 of 21 · partial in 12 · not supported in 5

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

The fix for the clients that need it

Needed in 17 of 21: Outlook Classic, Yahoo Mail, Yahoo Mail Android and 14 more.

Outlook Windows does not wrap a URL on word-break, word-wrap, or overflow-wrap. Insert ​ in a cell that has a width

instead 
<table role="presentation" width="100%" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td width="100%">
      https://example.com/&#8203;very/&#8203;long/&#8203;url?token=&#8203;abc123def456
    </td>
  </tr>
</table>
Show the original
before 
<span style="word-break: break-all;">
  https://example.com/very/long/url?token=abc123def456
</span>

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Your next question

Every feature in Fastmail · word-break in every client

Questions

How many email clients support word-break?
It works in 4 of 21, partial in 12, not supported in 5.
Does word-break work in Apple Mail?
word-break is partly supported in Apple Mail. Closest to Fastmail: Apple Mail, which agrees on 192 of the 235 features both are tested on.

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

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Real captures 14 Oct 2026 on 10 installs · caniemail (MIT) via @emailens/engine 0.18.22 · tested upstream 15 Feb 2022 · data last changed 10 Nov 2026 · Outlook (New) cells are the engine's mapping