uuencode is extremely old, mail clients are beginning to not understand it. I would try sending to a different email client first, to make sure it's actually going wrong, rather than just being received by a client which doesn't understand uuencode.
Thanks, the client is not a problem as it works from another system running Solaris (this one is Red Hat). I just found out about the mailx -a option which also attaches files. I guess I'll use this.
The sharutils package that used to provide uuencode was deprecated in rhel6, since mailx is able to send MIME attachments, as you have already figured out.