CITMTA & CIT FixCIT Tools

MTA:SA error code

MTA:SA error CD50

This MTA serial is already connected to that server.

Code
CD50
Where you see it
The connection dialog
MTA's own wording
Serial already connected
Family
CD codes

What it means

It usually means a second MTA on the same computer, or a session that has not timed out yet.

A CD code appears when a connection to a server fails, is refused, or ends. Most of them carry a second line with the server's own reason. MTA's own documentation gives this code as Serial already connected.

How to fix it

Work down the list and stop when it is solved.

  1. Close the other MTA

    Make sure no second MTA or GTA is still running, then wait a moment and connect again.

  2. Try the connection again

    Close MTA, open it again and connect once more. A single failed attempt can come from a restart on the server or a short break in your own connection.

Still stuck? The Fix tool reads MTA's own log on your computer and points at the matching steps. Nothing is uploaded.

Open the Fix tool

Other CD codes

Where this comes from

Official Error Codes catalog; full message and issuer remain necessary.

Meanings read from these sources on 5 September 2026 and written in our own words here.