Exchange 2013 Troubleshooting Expert Needed

I'm seeking an expert to troubleshoot and resolve issues with our Exchange 2013 server. Currently, email clients are unable to connect, impacting our communication.

Specifics:
- Email clients experiencing issues: Outlook, Mobile Email Clients, Webmail (OWA)
- Need to diagnose and fix connection problems

Ideal skills and experience:
- Extensive knowledge of Exchange 2013
- Proven experience in troubleshooting connectivity issues
- Familiarity with Outlook and mobile email client configurations
- Strong problem-solving skills and ability to work efficiently

Please provide your approach and estimated time for resolution.