>>I know it, but Preview correctly shows the text,
>>it is the Send that fails.
>>
>>I cannot put an operator of comparison in a text
>>what it is among two blocks PRE
>>
>>I send to you the full message.
>
>From my test, when I adjusted your message to only include code in PRE sections, not regular text, it went ok.

Of course.

But if you remove the second PRE block it work, but remove a piece of the text.

Example:

PRE BLOCK TEXT

next don't remove
SOMETEXT << SOMETEXT

next remove
SOMETEXT <
The problem pattern is < with a near right character,
but this is not a tag, a tag must to be within
a prefix and a suffix delimiter character.