Consider the following scenario:
- You have a Receive connector that is configured for a HubTransportserveror for an Edge Transport server in a Microsoft Exchange Server 2010 environment.
- You disable the tarpitting functionality on this receive connector.
- You enable Pipelining in Simple Mail Transfer Protocol (SMTP)
- A mail service uses Pipelining in SMTP to check the email addresses before forwarding mails between internal systems.
To work around this issue, try one of the following methods:
- Configure the tarpit interval to 1 if the mail service uses Pipelining in SMTP.
- Turn off Pipelining in SMTP.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.