Wordpress Site hosted on vultr not sending email

I deployed a server on vultr (one click wordpress install) but I am unable to send mail from my wordpress site. I have initially contacted vultr support and they have had my port 25 unblock and enable for mail sending. but I still cant send mail from my wordpress site. I head reinstall the server still upto no good. I contacted them again and they suggest I deactivate my Ubuntu Firewall which I did but the site still is not able to send mail.

on the wordpress I have used a plugin CHECK EMAIL to test the mail function but it was not delivered.

I re-contacted them again and this is what they had replied me with,

but I dont know how to use this specific information they have given to fix the present problem

Hello,

Thank you for your inquiry.

It seems that the there is no service listening on the related port.

nmap -p 25 45.77.76.173

Starting Nmap 7.60 ( https://nmap.org ) at 2018-11-24 15:19 EST Nmap scan report for 45.77.76.173.vultr.com (45.77.76.173) Host is up (0.0047s latency).

PORT STATE SERVICE 25/tcp closed smtp

Nmap done: 1 IP address (1 host up) scanned in 0.12 seconds

To cite Nmap's documentation: "The state is either open, filtered, closed, or unfiltered. Open means that an application on the target machine is listening for connections/packets on that port. Filtered means that a firewall, filter, or other network obstacle is blocking the port so that Nmap cannot tell whether it is open or closed. Closed ports have no application listening on them, though they could open up at any time."

https://nmap.org/book/man.html

Please ensure that the service is configured correctly and is listening on the port.

Please any suggestions will help. Thanks