The server was on a gray ip without ssl. Most likely could not establish a secure connection with the target server.
Currently, everything works on a white ip and with valid ssl certificates.
There is a strong lack of group (mass) operations, for example, to upload a template or a list of filtered csv/txt boxes and enter the data that needs to be changed into it. Logically, we need: creating/changing mailboxes, creating/changing synchronization tasks, changing quotas.