Knowledgebase

Your Exchange Server returns this error if the sender address is blocked by the sender filter of the Exchange Server: https://docs.microsoft.com/en-us/Exchange/antispam-and-antimalware/antispam-protection/sender-filtering?redirectedfrom=MSDN&view=exchserver-2019

Please deactive this filter or at least exclude SmartPOP2Exchange from ever being rejected.

SmartPOP2Exchange only deletes emails from the POP3 server if it has been successfully sent to the destination SMTP server.

If the SMTP server refuses the email more than 3 times it will be saved to the folder "<backup path>\DeliveryFailure" and a summary email will be generated and tried to be delivered instead.

This "error message" is caused by greylisting solutions.
For example, if you are using ESET for Server, even if you disable anti-spam capabilities in its configuration, it will not be greylisted.
To disable greylisting, the Exchange Server Transport Agent must be disabled by ESET: (in the Exchange Server PowerShell)
Disable-TransportAgent -Indentity "ESET FilterAgent

This is a limitation of the receive connector of the MS Exchange Server. It only allows a certain number of simultaneous connections from a single IP. The default value is 20.

You can query the value for your receive connectors on the Exchange Powershell:

Get-ReceiveConnector -Identity <connectorname> | fl MaxInboundConnectionPerSource

To change the value you can use the following command:

Set-receiveconnector - identity "CONNECTOR_NAME" -MaxInboundconnectionPersource 100

Please restart the Microsoft Exchnage Transport service after changing the values.

Please also see MSDN: https://docs.microsoft.com/en-us/Exchange/mail-flow/message-rate-limits?redirectedfrom=MSDN&view=exchserver-2019#message-throttling-on-receive-connectors

It seems you are missing the correct OLE DB Provider. 

To correct this you have to download the Access Database Engine 2016 from Microsoft. Make sure you download and install the 32-bit version.

Or use this direct download link.

The requested name is valid, but does not have an Internet IP address at the name server. This is not a temporary error. This means another type of request to the name server will result in an answer.

No such host is known. The name you used is not an official host name or alias. This is not a software error, another type of name server request may be successful.
Check that you have a name server(s) and/or host table configured. If you are using a name server(s), check whether the server host(s) are up (e.g. try to ping the server(s)). You could also try to resolve another host name you know should work, to check if the name resolution server application is running.

The server quota ran out. The server refused a connection because there are currently too many users connected to the server. Try again later.

No connection could be made because the target machine actively refused it. This usually results from trying to connect to a service that is inactive on the foreign host.

So either you tried to connect the wrong host, or the service (SMTP, POP3, IMAP) you're trying to contact isn't available. Check the destination address you are using. If you used a host name, did it resolve to the correct address? It's also possible that the remote services use a different port number.

A connect or send request failed because the connected server did not respond properly after a period of time. Check, if the destination address is a valid IP address. If you used a host name, did it resolve to the correct address?