Why are question marks displayed in my email client?

Question

Outlook

Hello!
There is a distance learning system (LMS) from which email is sent. In the exchange server network (I don’t know the version), letters are sent through it. All clients in the outlook network from 2007 to 2016, there are also mobile applications.
The letter is made up in html, not text (there are no problems with this in LMS). After sending, some employees (does not depend on the version of outlook) receive messages in this form (in the template, all text is in Cyrillic):

?????????????
?????"??? ???". ?????:
• ??? ?????? ??? ???;
• ??????" ???? ?? F001*750126;
• ????" ???? ??: VWksl2W0;
• ?????"µ?", ???????";
• ???? ????????????"??????";
• ??” ???? ??: ? ????? ?? ?????"???", ????????????" ???

Moreover, this is only 1/4 of the entire text of the message, the rest simply does not reach. What is even more surprising is that the list in the letter template is numbered, not bulleted. The subject line is correct.
Everything is done correctly in the letter template - there is a doctype, utf-8 encoding is registered in meta, styles in tags, etc.
Tell me why this can happen? Maybe someone had it.

Answer 1

All the same, it is worth once again carefully checking the encoding

Answer 2

Problems with layout for Outlook are the most kapets. Specify encoding always utf-8. You can take some editor like SublimeText and force Save Encoding As there and re-save it in utf-8 again.
I do not know how the exchange server works, but always and in all email clients, any letter is preprocessed before being displayed. Code analyzers remove/replace unresolved tags, properties, attributes, etc. and leave only what is allowed in their product there.
Outlook saw the light when I found out this fact: starting from the 2007 version, small software decided to use the engine for rendering letters from Word 2007. Before that, they used Trident, which was in ie6-7. In short, this garbage is even worse than ie6. So let's pat the melkosoft team on the hands for this great solution.