New Windows Update that could break connection to your smartermail

Problem reported by Chris Danks - 2/17/2025 at 3:46 AM

Submitted

I wanted to bring something to your attention about a change I found since the Feb 2025 windows updates.

Today we have had issues with a handful of servers giving errors such as An operation on a socket could not be performed because the system lacked sufficient buffer space

It ends up that windows now screws up when it has outbound TCP connections to ports higher than 5000, on our smartermail Servers we have on port 9998 which is over the 5000 number which caused the server to stop allow ANY kind of outgoing connection or get blocked after a period of time.

I found this new article: https://learn.microsoft.com/en-gb/troubleshoot/windows-client/networking/connect-tcp-greater-than-5000-error-wsaenobufs-10055

Smartertools should maybe add to their next update the reg changes

Here is a powershell script MaxUserPort.ps1 that I created. save/execute this on your server to fix this issue, your server will reboot.

Apply this to any remote windows server that connects to your smartermail on port 9998.

# Set registry path
$RegPath = "HKLM:\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters"

# Set MaxUserPort to allow ephemeral ports up to 65534
Set-ItemProperty -Path $RegPath -Name "MaxUserPort" -Value 65534 -Type DWORD -Force

# Confirm change
Write-Host "MaxUserPort has been set to 65534."

# Prompt for restart
$Restart = Read-Host "Restart required. Do you want to restart now? (Y/N)"
If ($Restart -match "[Yy]") {
    Restart-Computer -Force
} Else {
    Write-Host "Restart skipped. Please restart manually for changes to take effect."
}

6 Replies

Reply to Thread

Tan Replied

2/17/2025 at 7:55 AM

Hmmmm have you log a ticket to get their attention?

Jeffrey Werner Replied

2/17/2025 at 9:53 AM

Employee Post

Just from looking at the article you linked it looks to me like this should only really be effecting Windows Server 2003 and 2008. Smartermail currently requires Windows 2016 or higher and it doesn't look like there are any recent updates that would cause this issue. Are you running one of these older versions or did you experience this problem on a newer version Windows?

Jeffrey Werner

Software Developer

SmarterTools Inc.

www.smartertools.com

Chris Danks Replied

2/18/2025 at 3:57 AM

I am on Windows Server 2019

Kyle Kerst Replied

2/18/2025 at 9:49 AM

Employee Post

Do you know what update specifically caused this? I maintain servers across a variety of Windows Server versions that are all up to date as of this past weekend and so far I'm not seeing this on any of them. Was this server always 2019 or has it been upgraded over the years? Thanks Chris.

Kyle Kerst

Lead Internal Network/System Administrator

SmarterTools Inc.

smartertools.com