KARAM_SIDHU Found the SOLUTION
I would share here what was the root cause of this issue and how i manage to found it and act accordingly. So that, other members might attempt as such in case encounters the same issue.
What was the Root Cause:
Security Restrictions from the Web Host Server.
*The Server where my flarum script is hosted.
How did i Managed to find It out:
- I contacted Zoho Team [My Mail Host] and seek for an answer on the accurate SMTP Record to be utilised, As my Account is hosted on their US Data Centre based on checkings in my Zoho Account, therefore, I would like to know should i use smtp.zoho.com as per found in my Zoho Admin Console >> Mail Settings >> Configurations >> Outgoing SMTP column OR i should use either smtppro.zoho.com / smtppro.zoho.eu? They confirmed that, I should ideally use smtppro.zoho.com regardless of 465 over ssl or 587 over tls. At the same time, Checked with them if there is any restrictions on my Web Host IP which might occur especially if we are on a shared hosting due to previously misuse of their service by other users on the same server. They confirmed there is no restrictions found on the IP provided and there are unable to find logs associated with my attempt on the SMTP Connection. This clearly shows that somehow, the connection is not being established or it is not coming out from the Host itself.
- As i know i've already tried even with smtppro.zoho.com but yet failed, Thought that it is time to check if it is failing globally or specifically on my host itself only. The easiest method was used where i check my SMTP Status from a third party SMTP Checker by Mail Meteor [https://mailmeteor.com/tools/smtp-test] and found out that both 465 over SSL and 587 over TLS is Passing without any issue.
- Then, I attempted to produce error from browser [Inspect>>Console/Network] on my flarum url via front-end on signup and then via back-end at test mail, Found that both sides encountering an error known as "500-Internal Server error"
- Tried configuring same SMTP on my another website [Wordpress] that is installed on the same server and domain but separated by path [domain/blog] and found that SMTP is failing even at there and it is producing the same error as stated above .
- Contacted Web Host, Attached the references from the points above [1,2,3,4] and informed them that this is definetely a restriction from either their Security Infrastructure or their Set Permissions.
- The Web Host managed to find out the settings that might cause this issue and tweaked it accordingly in no time [Good Job credit goes to the Web Host Support Team], The first attempt upon tweaked setting itself has eliminated the error and emails are able to be delivered in no time [Super Fast].
Point to be highlighted:
Inspection [As per point 3]. My mistake was that, I decided to reproduce and inspect after certain period of time, and, i highly encourage to Prioritise Inspection. Inspect first, as it might primarily help in minimizing the circle of troubleshooting thus reducing the downtime over most issues that arise.
I would even like to thank all members that participated in this thread to assist directly and indirectly on resolving this issue. Thanks once again.