Slow emails sent in wordpress with smtp

[ninie1205]

I have a droplet with Ubuntu and wordpress set up, configured DNS records to work with gmail, installed a wordpress plugin called Wp Mail SMTP to handle the mailing system and whenever I test it, it takes more than 2 minutes to send an email through the contact forms on the website. If I switch back to php mail() everything works instantly. I have tried everything to make it work but to no avail, any idea where the problem resides?