Fix IIS 500 Error & Exchange

My IIS web server suddenly throws a “500 – Internal Server Error” every time it’s accessed. Nothing was altered in the IIS configuration before this started, yet the full error page appears instead of the site.

At the same time, after renewing the SSL certificate, Exchange Server 2013 has stopped delivering inbound email. Messages leave external hosts but never reach the internal mailboxes.

Here’s what I need addressed:

• Restore normal page load on the IIS site, eliminating the 500 error.
• Re-establish successful inbound mail flow on Exchange 2013 after the certificate renewal.

Acceptance will be a fully loading website and verifiable mail delivery tests (MXTools or similar) showing messages received internally.