mail/internal/mail/message.go
func (m *Message) SetDateHeader(field string, date time.Time) {
	m.header[field] = []string{m.FormatDate(date)}
}
func (m *Message) SetDateHeader(field string, date time.Time) {
	m.header[field] = []string{m.FormatDate(date)}
}
func ( m * Message ) SetDateHeader ( field string , date time . Time ) { m . header [ field ] = [ ] string { m . FormatDate ( date ) } }
// SetDateHeader sets a date to the given header field.
SetDateHeader sets a date to the given header field .