I too have the similar Query as what Vijaya has mention in her post.
My Team has written the custom SOAP based Web Service which will allow various application to connect through this service to send email.
When doing the performance testing using JMeter, I have few observation
1. When I send the 1 request to the server with the multiple EMAIL ID, the SOAP based service is able to send the email ..
2. When I send the concurrent request (50 request) and each request has 50 email (so in all 2500 email i.e. 50x50), then OpenEMM is not able to send email to the all the 2500 recipient.
What is surprising is that when I restart the sever and the point number 2 is executed I am able to receive the all 2500 email, but again if the rerun the same scenario then I observed high about of failure.
Wold request if any one can provide the insight on this issue as this will help us to understand the product better, so that we can leverage accordingly.