How many email clients support transition?

It works in 4 of 21, partial in 7, not supported in 10.

Does transition work in Fastmail?

transition works in Fastmail. Closest to HEY Mail: Fastmail, which agrees on 173 of the 235 features both are tested on.

transition in HEY Mail

Partial transition is partly supported in HEY Mail.

Buggy.

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

Which clients

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

What to do instead in HEY Mail

Transitions don't work in email; style the default state well

instead

8 lines

.button {
  /* Use the most visually appealing state as default.
     :hover is only supported in a few clients. */
  background-color: #6d28d9;
  color: #ffffff;
  text-decoration: none;
  font-weight: bold;
}

Show the original

before

7 lines

.button {
  background-color: #6d28d9;
  transition: background-color 0.2s;
}
.button:hover {
  background-color: #5b21b6;
}

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What HEY Mail does with transition

caniemail record, tested upstream 29 Mar 2024

Buggy. transition-duration is forced to 0 on a global reset style.

Your next question

Every feature in HEY Mail · transition in every client

Questions

How many email clients support transition?: It works in 4 of 21, partial in 7, not supported in 10.
What do I use instead of transition in HEY Mail?: Transitions don't work in email; style the default state well.
Does transition work in Fastmail?: transition works in Fastmail. Closest to HEY Mail: Fastmail, which agrees on 173 of the 235 features both are tested on.

To see what else in your email HEY Mail does not support, paste the whole email.

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caniemail (MIT) via @emailens/engine 0.18.22 · tested upstream 29 Mar 2024 · data last changed 10 Nov 2026 · Outlook (New) cells are the engine's mapping