Email Router - Incoming error - Index was Outside the bounds of the array

Hi,

I have a problem that occurs randomly in the Email Router, in Incoming Test Email.

<Data>#26090 - An error occurred while opening mailbox xxxxxx@xxxxxx.xxx. System.IndexOutOfRangeException: Index was outside the bounds of the array. at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add) at Microsoft.Crm.Tools.Email.Providers.ExchangeAutoDiscover.GetServerAddress(String emailAddress, String emailUserName, String emailPassword, ServiceLogger serviceLogger) at Microsoft.Crm.Tools.Email.Providers.ExchangePollingMailboxProvider.InitExchangeConnector() at Microsoft.Crm.Tools.Email.Providers.ExchangePollingMailboxProvider.OpenMailbox() at Microsoft.Crm.Tools.Email.Providers.CrmPollingMailboxProvider.Run()</Data>

If I restart the service of Email Router, the problem disappears.

Suggestions?

Thanks for your help

Nichi