Mailcow Server Troubleshooting on CentOS

I am encountering connection issues with my Mailcow email server after an update. The problem seems to be that Nginx cannot connect to an upstream server or other services which may not be ready yet. This could be normal if Mailcow was just installed or updated, but it has been several minutes.

I am running my Mailcow on a CentOS operating system. I've checked the logs and do have specific error messages, but I need a professional to help interpret them and resolve the issue.

Ideal skills and experience for the job include:
- Extensive experience with Mailcow server
- Proficient in troubleshooting Nginx issues
- Familiar with CentOS operating system
- Good understanding of server logs and error messages
- Ability to perform server maintenance and updates
- All work done via Anydesk
- No SSH