Unfortunately, that probably means that this is not compatible with Zen Cart 1.3.7. The attachment part of the zen_mail function was listed as an experimental feature in the Zen Cart code, which probably means it was added in 1.3.8.
What you'll need to do to make this work with 1.3.7 (without the attached PDF slip, you need 1.3.8 for that) is to find the zen_mail function and then rewrite one line of code to fix this. The line of code you will need to rewrite is on line 475 of send_pos.php. It looks like this:
zen_mail($adresdo,$adresdo,$tematk,$newzawartosc,PO_FROM_EMAIL_NAME,PO_FROM_EMAI L_ADDRESS,NULL,NULL,$pdffilename);
You'll need to search for where this function is defined. Do that by going to Admin-Tools-Developer's Toolkit and searching for "function zen_mail" without the quotes. Check that file out and see the variables that are defined in this function. That will help you rewrite the code on line 475 of send_pos.php. If you can't figure it out, post the code you find by searching with the developer's toolkit and I will tell you how to change line 475 of send_pos.php.
By the way, the configuration stuff wasn't added by me. All of the configuration stuff was in the SQL update you installed originally. You can find it under the Extras and Configuration menus in Zen Cart Admin.
By the way, I highly recommend you update to 1.3.8. There are tons of bug fixes and new features. Well worth the time and effort!
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