PHPMailer performance

I’ve configured Trellis to use MailGun and have noticed PHPMailer performance is quite slow.

I’ve gathered this from New Relic which I have running on the production server. I’m using WooCommerce and was analysing page performance, particularly the checkout page which sends two emails upon completion (external to the customer and internal to me) and the mailPassthru method took in total around 3.3 seconds to send both emails.

I don’t think trellis would have anything to do with this but is there any other way to speed this up or is this normal?