Selector or pseudo-class · data last changed 10 Nov 2026
:class-selector in email clients
Works in 17 of 21. Not supported in Proton Mail. Partial in Gmail Android and Gmail iOS. Untested in Superhuman.
Your reader in Proton Mail sees the email without :class-selector, even if it looks right where you tested it.
caniemail (MIT) via @emailens/engine 0.18.22
What to do instead in Proton Mail
There is no drop-in fix for :class-selector in Proton Mail. Design so the email still reads without it.
No signup · Five clients free, Outlook Classic included · All 21 with an account
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:class-selector is not among the 24 features we have screenshotted on real installs. The ones we have →
All 21 clients, problems first
| Client | Support |
|---|---|
| Proton Mail | Not supported |
| Gmail Android | Partial See caveat 1 |
| Gmail iOS | Partial See caveat 1 |
| Superhuman | Untested |
Works in 17: Gmail, Outlook 365, Outlook (New) and 14 more. Show all
| Client | Support |
|---|---|
| Gmail | Works |
| Outlook 365 | Works |
| Outlook (New) | Works |
| Outlook Classic | Works |
| Outlook iOS | Works |
| Outlook Android | Works |
| Outlook for Mac | Works |
| Apple Mail | Works |
| Apple Mail iOS | Works |
| Yahoo Mail | Works |
| Yahoo Mail Android | Works |
| Yahoo Mail iOS | Works |
| Samsung Mail | Works |
| Thunderbird | Works |
| HEY Mail | Works |
| AOL Mail | Works |
| Fastmail | Works |
Caveats (1)
- 1. Gmail Android, Gmail iOS: Partial. Not supported with non Google accounts.
Caveats as recorded by caniemail (MIT), one entry per wording.
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