Letter layout testing

Question

css

Good morning.
I am interested in online services for quick testing of letter layout.
I haven’t seen it in RuNet, in the bourgeois Internet, Google gave out only paid ones.
Personally, I myself used the tester built into the paid pardot service , but purchasing a package of this service for the sake of testing is extremely unreasonable.
Who used what services? Share links and opinions.

Answer 1

Try litmus.com - a lot of customers.

Answer 2

Before testing the layout, I usually check the validator.w3.org markup because QWIRKS -mode and everything that follows from it affects not only the browsers directly, but also the rendering of pages in the mail client.