mail-proxy compatibility option enable

Function

The mail-proxy compatibility option enable command enables the mail proxy compatibility option. After you enable this function, the mail proxy no longer changes the ACK time window to 0 in domain server handshake.

The undo mail-proxy compatibility option enable command disables the mail proxy compatibility option.

Format

mail-proxy compatibility option enable

undo mail-proxy compatibility option enable

Parameters

None

Views

System view

Default Level

3: Management level

Usage Guidelines

By default, the mail proxy compatibility option is disabled.

As an mail proxy, the FW establishes a TCP connection with the server. The server determines whether the FW sends subsequent window update packets based on the ACK packet.

If the TCP window field value in the ACK packet sent from the FW is 0, the server waits for subsequent window update packets from the FW.
- If the server receives subsequent window update packets from the FW, traffic continues.
- If the server does not receive window update packets from the FW, traffic between the server and FW is interrupted.
If the TCP window field value in the ACK packet is not 0, the server does not wait for window update packets, and traffic continues.

On special networks where the FW sends window update packets to the server but the packets are discarded during transmission, the server interrupts traffic because it does not receive (should receive) window update packets, resulting in anomalies. To resolve this problem, you can run the mail-proxy compatibility option enable command, so that the FW changes the TCP window field in the ACK packet to a non-0 value and does not send window update packets.

Example

# Enable the mail proxy compatibility option.

<sysname> system-view
[sysname] mail-proxy compatibility option enable