I am trying to setup a web based email client on Digital Ocean to allow me to access my email in my preferred manner. I noticed that I am unable to send email over SMTP/SSL (port 465) from my Digital Ocean hosted web mail client to my Zoho Mail account.

I have already lifted the iptables on the hosted instance but am unable to use SMTP/SSL to use the hosted web mail to access Zoho Mail.

I tested the web mail on a test environment outside of Digital Ocean and it is able to access the Zoho Mail over SMTP/SSL.

Is there some sort of restriction of SMTP/SSL traffic for any hosting providers ?

How should I resolve this problem ?