Welcome banner stopping scp

Commands running on top of the ssh transport do not expect large amounts of output before they can start their server. This will affect a number of utilities.

The solution is to have your administration team print the message only if stdout is connected to a terminal.

if ( $?prompt ) then
    echo "Secure machine message..."
    echo "More warnings"
    echo "Etc."
endif

Better still, you wouldn't put this in .cshrc at all, but instead the message content itself would go in /etc/issue.net, which is displayed before login. This may need enabling in /etc/ssh/sshd_config though, with a line like this:

Banner /etc/issue.net

You cannot print anything in non-interactive session. That breaks any clients that use a strict protocol, such as SFTP or SCP.

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Use /etc/motd (which is used for interactive sessions only).

Or use sshd_config directive Banner.

Or test for interactive session before printing anything (e.g. by testing an existence of TERM or prompt variables).

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For background, see my answer to Server Fault question SSH MOTD per user.