In LANs, emails are often used by people, but due to the influence of factors such as the system platform, networking method, topology, etc., data transmission failures can be caused, making emails and their attachments unable to be sent normally. Some workstations in the author's company's LAN use WinXP systems, but they have never been able to send emails, which seriously affects the effective use of the LAN. If it cannot be solved, then each machine equipped with a WinXP system can only reinstall Win98 or other systems, which will cause a lot of duplicate work and waste of resources. After our efforts, we finally found a solution.
The following is a WinXP system as an example to illustrate how to modify the registry to make the network smooth and emails can be sent normally. Our LAN access to the Internet uses downlink asymmetric transmission method connected to satellites. With Winroute as the proxy software, multiple computers in the LAN share DirectPC connections. Because the expected data packets of DirectPC do not match the size of the data packets sent and received by the client, the client blocks the data reception and cannot send emails. In order to send emails, the WinXP system registry needs to be modified as follows: "HKEY_LOCAL_MACHINE＼System＼CurrentControlSet＼Services＼Tcpip＼Parameters＼Interfaces＼{…}＼MTU”. The {…} under Interfaces requires the user to determine which network card branch is the corresponding network card branch. Generally, it contains content such as the local IP address or gateway. Each branch in the WinXP registry has a lot of content, so you need to carefully distinguish it and correspond to the network settings of the server. After finding this branch, create a new key "MTU" of type "DWORD", and the value is the decimal number "1466". After the modification is completed, restart the machine and send emails normally, and there is no problem with attachments.
Also, it should be noted that the main server registry should also be modified accordingly. If other clients use other Windows systems, they should also modify their registry so that their emails can be sent normally. The specific reference is as follows:
Win2000
HKEY_LOCAL_MACHINE＼System＼CurrentControlSet＼Services＼Tcpip＼Parameters＼Interfaees＼{…}＼MTU (DWORD value: 1466)WinNT
HKEY_LOCAL_MACHINE＼System＼CurrentControlSet＼Services＼"ejthernet_adapter"＼Parameters＼Tcpip＼MT (DWORD value: 1466)Win98/Me
HKEY_LOCAL_MACHINE＼System＼CurrentControlSet＼Services＼Class＼NetTrans＼OOx(x may be 0, 1, 2…)＼MaxMTU (String value: 1462)
The above also needs to be determined before making modifications. After modification, the client host can send emails and their attachments. If the server's registry creates a new MTU value, the client MTU or MaxMTU value should not be greater than the server-side value (if present). The value range can be modified according to actual conditions to achieve the best matching rate. After the modification is successful, export the registry for backup, which can be prepared for emergencies.