What does "Couldn't connect to..." mean?

The complete error message is e.g. "microsoft_exchange: Couldn't connect to 10.1.0.100".

I.e. sync.blue® tries to connect to your system from "outside" (from the public internet / "behind your firewall") to synchronize the contacts. This connection is technically not possible and breaks after a certain time.

Common causes are:

• A private IP address was entered (e.g. 10.1.0.100 or 192.168.0.100) instead of the own public IP address of the own Internet router. Please connect sync.blue® exclusively via the public IP address and the public port (tip: port forwarding). Usually, an IT system house / the IT department can set this up with little effort and provide this info.
• The customer's firewall blocks the requests from sync.blue®. Please unblock the IPs of sync.blue® in your firewall.
• The customer software is actually not available for a short time (e.g. due to an update).
• The own software must not be reachable via internet for security reasons. Read more solutions here.