When you encounter the error "SMTP is not working on the server," it suggests that the SMTP (Simple Mail Transfer Protocol) functionality on the server is encountering issues, preventing it from sending or relaying emails. SMTP is responsible for sending emails from one server to another over the internet, making it a critical component of email communication.

The causer of given error:

• Faulty SMTP credentials
• Firewall obstructing SMTP connection
• Unsuitable authentication protocol
• Lack of SMTP authentication activation on the sender's account
• Wrong choice of port

The solution to given error:

• Authenticate your SMTP credentials by double-checking against the provider's recommendations. Take particular care in selecting the correct communication port; some SMTP servers function exclusively on certain ports such as 587 while rejecting others like 465 (utilize TLS for establishing contact).
• Guarantee that the sender's account possesses active SMTP authorization before proceeding further.
• As a last resort, consider deactivating both firewalls and antivirus software temporarily to determine whether they interfere with the SMTP process.