In VirtueMart 3.4.3 10014, we found a bug in in the Question about product function. After using this feature, an email subject with strange characters will come: 

Rudolf Baláš recommend to you: Související produkty rozšířené pro Virtuemart

We've found that in this version added / forgot dev team in model product custom function vmHtmlEntities

As a result, the entire subject of the e-mail becomes a jumble of characters using hook and comma characters, which causes the e-mail to be included in spam rather than working properly.

The solution is very simple:

In file:

administrator/components/com_virtuemart/models/product.php

find the code (around line 1085):

$child->product_name = vRequest::vmHtmlEntities ($child->product_name);

and comment out:

// $child->product_name = vRequest::vmHtmlEntities ($child->product_name);

You won't find this code in a lower version (e.g. VirtueMart 3.4.2)