Execute sending the mail in a task queue. Allowing the microflow to continue and close the page.
Hi Harshraj,
For performance optimization, you can go through Mendix documentation,
You can find the link for the documentation by Clicking here. This may help you to optimize your application performance.
And for the Emails, as Rene said, you can use a task queue, and send the email in a parallel thread.
Hope it helps!