CSS property · data last changed 10 Nov 2026
text-decoration-thickness in email clients
Works in 7 of 21. Not supported in Gmail, Gmail Android, Gmail iOS and 10 more. Untested in Superhuman.
Your reader in Outlook Classic sees the email without text-decoration-thickness, even if it looks right where you tested it.
caniemail (MIT) via @emailens/engine 0.18.22
What to do instead in Outlook Classic
- Not supported, but the proprietary
text-underline-styleproperty can be used instead with the keyword valuethick.
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text-decoration-thickness 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 Android | Not supported |
| Gmail iOS | Not supported |
| Outlook 365 | Not supported |
| Outlook (New) | Not supported |
| Outlook Classic | Not supported See caveat 1 |
| Outlook iOS | Not supported |
| Outlook Android | Not supported |
| Outlook for Mac | Not supported |
| Yahoo Mail | Not supported |
| Yahoo Mail Android | Not supported |
| Yahoo Mail iOS | Not supported |
| AOL Mail | Not supported |
| Superhuman | Untested |
Works in 7: Apple Mail, Apple Mail iOS, Samsung Mail and 4 more. Show all
| Client | Support |
|---|---|
| Apple Mail | Works |
| Apple Mail iOS | Works |
| Samsung Mail | Works |
| Thunderbird | Works |
| HEY Mail | Works |
| Proton Mail | Works |
| Fastmail | Works |
Caveats (1)
- 1. Outlook Classic: Not supported, but the proprietary
text-underline-styleproperty can be used instead with the keyword valuethick.
Caveats as recorded by caniemail (MIT), one entry per wording.
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