See this post for details on troubleshooting the headers already sent error:
the error is pointing to line 1:
output started at /home/lactacyd/public_html/contacto-pronet-lactacyd.php:1
This usually happens if the file is saved with the Unicode BOM Signature enabled. See the end of the post I linked to for details on checking the BOM Signature.
There is no attachment, please compress the contacto-pronet-lactacyd.php file to a zip archive.