CSS property · data last changed 10 Nov 2026
[required] in email clients
Works in 7 of 21. Not supported in Gmail, Gmail iOS, Outlook 365 and 9 more. Partial in Gmail Android. Untested in Superhuman.
Your reader in Outlook Classic sees the email without [required], even if it looks right where you tested it.
caniemail (MIT) via @emailens/engine 0.18.22
What to do instead in Outlook Classic
There is no drop-in fix for [required] in Outlook Classic. Design so the email still reads without it.
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[required] is not among the 24 features we have screenshotted on real installs. The ones we have →
All 21 clients, problems first
| Client | Support |
|---|---|
| Gmail | Not supported |
| Gmail iOS | Not supported |
| Outlook 365 | Not supported |
| Outlook (New) | Not supported |
| Outlook Classic | Not supported |
| Outlook for Mac | Not supported |
| Yahoo Mail | Not supported |
| Yahoo Mail Android | Not supported |
| Yahoo Mail iOS | Not supported |
| HEY Mail | Not supported |
| Proton Mail | Not supported |
| AOL Mail | Not supported |
| Gmail Android | Partial See caveat 1 |
| Superhuman | Untested |
Works in 7: Outlook iOS, Outlook Android, Apple Mail and 4 more. Show all
| Client | Support |
|---|---|
| Outlook iOS | Works |
| Outlook Android | Works |
| Apple Mail | Works |
| Apple Mail iOS | Works |
| Samsung Mail | Works |
| Thunderbird | Works |
| Fastmail | Works |
Caveats (1)
- 1. Gmail Android: Partial. Only supported with non Google accounts.
Caveats as recorded by caniemail (MIT), one entry per wording.
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