queue method
Queue the email for background sending
Implementation
Future<void> queue() async {
validate();
final htmlContent = await _renderTemplate();
final mail = mailer.Mail().toMany(to).subject(subject).html(htmlContent);
if (cc.isNotEmpty) mail.ccMany(cc);
if (bcc.isNotEmpty) mail.bccMany(bcc);
await mail.queue();
}