Did you send the email to a hotmail or other web-based email account? (as in you dont require a client like MS OE or Mozilla TB) If you did then the receipt request may become obsolete - not all web-based email accounts support them as far as I know
OnePlus 5T review: Hands-on
Illustrator Andrés Lozano on his improv line work, brazen use of colours & hand sketching
iPhone X review
Comment envoyer gratuitement des gros fichiers ?