You can test for port 25 blocking anytime by going to any folder and using the Email Page option from the Tools drop-down. Make sure your preferences in your profile are not set to "Use My Email Client for 'Email Page'" when you test. Using the test email from the Web-based Project Insight interface will ensure that we test through the currently configured SMTP server from the Web application.
Next, set an auto-alert for your email address (by email address, not you as a user) on a folder for new items created and create a new item in that folder. Auto-alert email may take several minutes to send, so wait awhile for this test auto-alert before deciding that it is not working.
The above two paragraphs test both the Project Insight Windows Services and the Project Insight Web Application to make sure they can use SMTP. If either doesn't work, you should see an error logged in the Event Viewer -> Application to help you determine more specifically what happened when the email send attempt failed.
If Project Insight Windows Services is not working, you should turn off the service and set it to "manual" because it's only purpose is to send email. There's no reason to clutter the Event Viewer with an error every few minutes for something sending email if we know it's being blocked. Remember to turn it back on for testing once you think you have the SMTP issues fixed.