Hi frank at luray,
Does this issue occur with any file that you try to send, or do you find that it's specific to one file? If it's a file-specific error, and the file is large, please try sending the file via Adobe SendNow. (You can sign in to Adobe SendNow at Sign in or create an account | Adobe SendNow using the same credentials you use to sign in to Adobe Send.)
Please let us know how it goes.
Best,
Sara