I’m having trouble with email delivery using Mailgun’s API in my .NET Core application. Everything works perfectly when I test it locally on my development machine. However, once I deploy the application to my production server, I encounter an SSL connection error.
The exact error message I receive is about SSL connection establishment failure. I’m not certain whether this is related to my server’s SSL configuration, something on Mailgun’s end, or potentially a Cloudflare configuration issue.
Has anyone experienced similar problems with Mailgun API calls failing in production while working fine locally? I’ve been troubleshooting this for several days without success.
Sounds like a certificate validation issue - super common in production. Your server’s probably behind a corporate firewall or proxy that’s intercepting SSL traffic, which breaks the certificate chain when hitting Mailgun’s endpoints. I ran into the exact same thing where dev worked perfectly but production kept throwing SSL errors. Fixed it by updating the server’s certificate store and making sure all intermediate certificates were installed properly. Also check if your hosting provider has any weird SSL requirements or restrictions for outbound API calls. Production servers often have stricter security policies that block certain certificate authorities or need extra config steps you don’t need locally.
check your server’s datetime settings first - I had this exact problem and the production server clock was off by 20 minutes, which broke ssl validation. Mailgun’s strict about cert timestamps. also try adding ServicePointManager.SecurityProtocol in your startup code to force modern tls versions.
I encountered a similar issue with the Mailgun API when deploying my .NET Core application. The problem stemmed from the server using an outdated TLS version, which resulted in SSL handshake failures. Locally, everything worked seamlessly due to using a more recent version. I resolved this by enforcing TLS 1.2 for outgoing connections in my server settings. Additionally, it’s wise to ensure that your firewall isn’t obstructing Mailgun’s ports, as that can frequently lead to issues in production environments.