The symptoms explained result from the email server reacting as if it were being attacked or abused. The email server may even suppress actual error messages or give error messages that are too ‘general’ to denote a specific problem. Sometimes, the email server may even blacklist the FocalScope hosting server IP address either permanently or for a certain duration, causing FocalScope to stop sending and receiving emails.
Unlike email clients such as Outlook, which run on individual computers with distinct IP addresses, collecting emails for their respective users, FocalScope collects emails for all the accounts which are configured from the IP address where the FocalScope instance is hosted. This may very often lead the email server misinterpreting this as an attack since a lot more traffic is generated from a single IP address.
The most likely reason for this is some restriction on the email server such as:
Please note, connection refused and Login failed error messages may be indicative of actual problems not related to the scenario detailed in this article. Please see the Additional Information section (below) for other potential causes of these errors.
Whitelist the FocalScope application server IP address on the email server, and set any traffic limits to unlimited.