EDIT: For Css Calc(), I would say that maybe you could use it in Apple Mail or iOS native client, but even those are not likely. All others have almost no CSS3 support. See https://www.campaignmonitor.com/css/ for a pretty good list of available CSS and HTML tags in HTML email. Admittedly, this is not the Be-All list of what works in HTML emails, but as Calc() is not even listed, I would view this as a no.
EDIT2: Did a simple table html email to check results using Email On Acid and got surprising results.
https://www.emailonacid.com/app/acidtest/display/summary/hM0n3RkP89L9bfWOtXlTpQR238VwFFotgq4PkQpvBOpUf/shared
Basically looks like it works on:
Apple Mail
Outlook 2011 (apple version)
Thunderbird
Android 4 native client
iOS native
Aol (browser dependant)
Outlook.com (browser dependant)
(GMail will also accept it! - but must be inlined)
This is better then I thought, but considering, it still doesn't seem to be that elegant a solution as it fails completely in many of the popular email clients - including every webmail app (GMail app, Yahoo app, etc). It may be a viable solution depending on your audience, but in general, I would not recommend.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…