> I think email would be a lot better if plain text were the only format possible.

When writing longer emails it helps to be able to emphasis words, section the email, quote, create bullet lists and hide long links behind a title. All of these would work nicely if email clients would support (and default to) markdown.

Attachments are sufficient for images, but with markdown I could still inline them when it makes sense.

Fonts/colors are very frustrating every time I compose emails and copy/paste text.

I agree, I think markdown would be a nice compromise between plain text and ugly HTML.

Strongly disagree. I can communicate with my colleagues much better if i can embed pictures, math equations, use highlighting, etc.

> if plain text were the only format possible

Hard to enforce? <p>this</p> is text too.

A few <p>tags</p> in a larger text are ugly but not too bad. Most HTML e-mails are 200 lines of tag soup without any content, then 100 lines of content wrapped in several layers of tags and finally 50 more lines of tag soup without any content.

Don't forget that the parts you are trying to read are actually text embedded in images

Monospaced?

There are probably cases where plain text email is enough (linux kernel development seems to be doing fine), but once you enter corporate world HTML and all its goodies bring a lot of benefits.

(HTML) "Please have a look at this table (table pasted inline to email) and compare the results with previous run (another table inline)"

(plain text) "Please have a look at attached table (table1.xlsx) and compare the results with previous run (table2.xlsx)"

Sure, both bring the same information but the former gives you all the information immediately.