How to identify the name of my smtp-mail host dynamically?

Question

Hi,
I want to send an email from my system which has an internet connection.
I don't know how to identify and mention the name of my smtp server ie; the smtp-host name that should be mentioned in my propetries object 'props' as props("mail.smtp.host","smtphostname");
I want this program to work on other systems also,ie; It should dynamically find out what is the smtp-email host for the computer on which the program is running and set the smtp-host name in the 'properties' object dynamically.
I will be thankful if anybody sends me code to solve this problem.
Thank u in advance,
Ravi.

Answer 1

Write a mail scan to look for typical settings
such as domain, mail.domain, smtp.domain, smtp.mail.domain
where domain is after @ in an email address
Have a SocketSearch class that uses non blocking via java.nio.channels.*
so it can be interruptable and scan for these typical mail settings on default port 25 - The code using these interruptable socket can each be threaded to find the host/port and should find it in seconds
Once found, store the settings in a configuration so you don't have to scan again unless it doesn't work anymore...
If can't find the socket host/port via typical settings, next use a Java class that does a nslookup based on MX records - For example if you type "nslookup -type=mx javasoft.com" and you get mail exchanger = mail.java.sun.com and if you "telnet mail.java.sun.com 25" - you can see the port is open for sending emails.
No expert in MX records for a domain to find the exact one and someone else can share some light on this...