Internationalisation
Unicode, language, direction, and international addresses.
Required
UTF-8 message content
Encode international text consistently as UTF-8 across headers and bodies, with MIME declarations and transfer encodings that preserve every character.
RequiredMessage language and text direction
Declare the message language and mark bidirectional runs so pronunciation, punctuation, numerals, and reading order remain correct.
RecommendedInternationalized email addresses
Accept and preserve Unicode mailbox addresses only when every validation, storage, SMTP, and support path handles SMTPUTF8 safely.