Já jsem to zkusil takto

mail("xxxxxxx@xxxxxx.cz","sublekt ","techtlemechtle",$attachment    = chunk_split(base64_encode(file_get_contents($soubor))));

a výsledek soubor přenesen ale textovém formátu kousek souboru
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9xVNIlEhf5qnEnajlGO3Uzdh8VmxCPJ65P0piufVefStea47Dg1BNL2nKMYRzVC6TMiED+IfzoUr
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RViHUUaAO7Uw0ALTWoAjpKJDFppFQtgG0VQxxplFyR4qSgCCXrUPFJxGOprVb0QEeNwxU/WoaQAO
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