.NET API cannot send emails through Carbonio, or it takes a long time, even though it is on the same network.

Hello, I have a strange problem with my network.

I have an app that sends emails via the .NET API through Carbonio. The server for this API is on the same network, its IP is 10.2.0.195 removed link Carbonio's IP is 10.2.0.14 removed link When the API server sends emails, with or without attachments, it takes a long time to send, up to 10 minutes. However, when the messages are sent from a server in another network segment, including another VLAN, passing through a Fortigate firewall, the server with the IP 10.2.2.13/24, they are sent quickly, in seconds.

We have already looked at all the logs, both on the API server and on Carbonio, but we have not found anything that explains this behavior.

Does anyone have any ideas that could help?