Space/spacing in From email addresses not delivering to Hotmail

According to RFC 5322, spaces in email addresses are invalid. RFCs set standards and are not law, however currently Hotmail takes this very seriously and has a zero-tolerance policy when it comes to email addresses with spaces.

Emails sent with a from address with spaces e.g. space [e-mail] to any Hotmail address will bounce. To ensure these emails deliver to Hotmail addresses, you must either add in an underscore e.g. [e-mail] or remove the space e.g. [e-mail].