About Port number in JavaMail

[Chanakya Gupta]

Help us solve this.

We have a web application hosted on tomcat-7, say
this is Server-A. This web application is sending an
email from GMail SMTP host to the users email address.

The below code are the Properties settings.

Properties props = new Properties();
String SMTP_HOST_NAME = "smtp.gmail.com";
[color=darkred]String portId = "465";[/color]
                  props.put("mail.smtp.host", SMTP_HOST_NAME);
                  props.put("mail.smtp.auth", "true");
                  props.put("mail.smtp.user",SMTP_AUTH_USER);
                  props.put("mail.smtp.port", portId);
                  props.put("mail.smtp.starttls.enable","true");
                  props.put("mail.smtp.debug", "true");
                  props.put("mail.smtp.auth", "true");
                  props.put("mail.smtp.socketFactory.port", portId);
                  props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
                  props.put("mail.smtp.socketFactory.fallback", "false");

Our doubt is, why this code works fine only when
the port 465 is open on Server-A. We understand
from the JavaMail docs that 465 pertains to the
port on smtp.gmail.com. Why 465 to be open on
Server-A when it is not sending any emails ?

Thank you in advance.

[Chanakya Gupta]

After some search, got this satisfactory
answer from Wikipedia. Thank you all
for your patience. Quoting the answer
from Wikipedia.

http://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol
"

...While electronic mail servers and other
mail transfer agents use SMTP to send
and receive mail messages, user-level
client mail applications typically use SMTP
only for sending messages to a mail server
for relaying....

"

Since, our web application is user-level client
mail application it uses SMTP and hence port
465 is to be opened.