Be more lenient before sending notifications on network path errors

Occasionally (maintenance, ...) the target location can't be contacted due to network timeouts or similar, resulting in a message like this:

The network path was not found

It should be checked if this specific error can be caught and the corresponding notification could be delayed until this happens for a few attempts in a row to prevent an email flood when e.g. a file server is rebooted and therefore not available.