Hi, I run two digitalocean droplets. One is an Ubuntu 16.04 which I run as a mailinabox email server. This has run with no problems for many years and handles incoming and outgoing email for my personal emails and a handful of friends. The other one is a DO marketplace cyberpanel droplet, on which I run a few websites, mostly wordpress based.
I normally configure my wordpress sites on the cyberpanel droplet to send email via the external SMTP server on my other droplet, it previously worked fine. But this cyberpanel droplet has stopped being able to connect to my SMTP server (or any external SMTP server). I have checked firewall etc and all settings i can think of.

I just want to check whether there is something on DigitalOcean’s end that is blocking this connection? It is really essential for me to get this working.