Error in sending test mail at Hudson Email Notifications - email

Question

I could successfully send e-mail notification in Hudson using gmail as the smtp server.
But when I try to configure our own smtp server, it gives the following error when trying to send the test mail:
Failed to send out e-mail
javax.mail.MessagingException: Exception reading response;
nested exception is:
javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?
Are there any special configurations with the e-mail notifications???
Edit:
Also does it require enforcing the security certificate and if so is there a way to achieve it???
Thanks

Answer 1

Please try using the following settings:
SMTP SERVER : smtp.gmail.com
use SMTP Authentication : true
use SSL : true
SMTP port : 465

Answer 2

I had this problem too. My solution was to make all the necessary configuration (check ssl box and stuff) and CLICK THE SAVE BUTTON before use the test mail.
i just had this issue before clicking the save button.

Answer 3

Changing the SMTP port from 587 to 465 also resolved this issue for me, even though I'm using an alternative SMTP service:
SMTP server: smtp.mandrill.com
Use SMTP Authentication: true
Use SSL: true
SMTP Port: 465
From what I can tell (disclaimer: I am by no means a Hudson/Jenkins expert)
the Hudson/Jenkins email plugin supports SSL encrypted SMTP communication - however this implementation requires that communications are encrypted from the get go.
When connecting on port 587, the server on the other end may expect a STARTTLS command (see this SSL vs TLS vs STARTTLS article). This command is sent using plain-text to 'upgrade' the connection to use SSL/TLS.
Hudson/Jenkins instead attempts to start negotiating SSL on port 587, which is promptly rejected, resulting in the following error:
javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?
I also tried adding additional JAVA options "-Dmail.smtp.starttls.enable=true" (configured in /etc/default/jenkins on Unbuntu) to enable TLS:
JENKINS_JAVA_OPTIONS="-Djava.awt.headless=true -Dmail.smtp.starttls.enable=true"
Unfortunately this didn't resolve the issue for me.
After changing the port to 465, the SSL negotiation occurred correctly and the communication succeeded.
Hope that helps.