I've been trying to send an e-mail using PHPMailer but have been getting a "504 Gateway Time-out" error.

Did a bit of research and I think it's because nginx is trying to use IPv6. I thought the solution was to try to make it use IPv4 was the solution.

Tried to do the following already:
echo 'Acquire::ForceIPv4 "true";' > /etc/apt/apt.conf.d/99force-ipv4
echo 'precedence ::ffff:0:0/96 100' >> /etc/gai.conf
service nginx restart

Still getting the same issue and I can't find anything else that I could try.