Why do letters disappear in mail (e.g. letter)?

Question

Email

When sending a letter through the procedure, a mail arrives in which there are no certain letters. As I found out, only the letters that are near the brackets "" disappear. Maybe someone came across it? This happens on different PCs, different browsers, viruses, third-party software, browser add-ons do not affect this.

Answer 1

Disappeared, perhaps due to the support of Unicode characters when writing/storing in the table, which are on code points (code points) outside of ASCII/Latin1.

Answer 2

Look at the source of the letter (in gmail, for example, you can see it through Show original, other mailers usually also have buttons) what your mssql has done there.
What is the transfer-encoding of the message?