fix: removed invalid options for the sendmail transport (#8576)

* Removed invalid options for the sendmail transport that were causing Nodemailer to return the SMTPTransport instead.

* Removed options for rate limiting in admin email interface. Added new option for toggling whether to use pooled connections.

src/emailer.js

@@ -25,9 +25,6 @@ Emailer.transports = {
 	sendmail: nodemailer.createTransport({
 		sendmail: true,
 		newline: 'unix',
-		pool: true,
-		rateLimit: meta.config['email:sendmail:rateLimit'],
-		rateDelta: meta.config['email:sendmail:rateDelta'],
 	}),
 	smtp: undefined,
 };
@@ -66,7 +63,9 @@ Emailer.setupFallbackTransport = function (config) {
 	winston.verbose('[emailer] Setting up SMTP fallback transport');
 	// Enable Gmail transport if enabled in ACP
 	if (parseInt(config['email:smtpTransport:enabled'], 10) === 1) {
-		var smtpOptions = {};
+		var smtpOptions = {
+			pool: config['email:smtpTransport:pool'],
+		};
 
 		if (config['email:smtpTransport:user'] || config['email:smtpTransport:pass']) {
 			smtpOptions.auth = {