This works for me, I just had to quote the email address :
"mailto:"& "XYZ" &
URL has a character limit, just for you to be aware.
Any reason for not using built-in Send Mail scrip step?
Is there a reason you're using Open URL as opposed to "Send Mail"? The latter has an option to send via the default mail client, and it's much more reliable than using Open URL.
Even more reliable/controllable would be an email plugin.
The character limit in URL is around 2000 characters.
What is you default email client?
Outlook. The built in mail script has never worked on server reliably for us. I will try it again now that we are on 14.
I do not think FMS 14 will help, but try anyway. I suspect you have a problem with Outlook settings, something may be set by a Network Administrator or as a default, which prevents external programs sending the emails through Outlook.
If it is the case, Mike's suggestion of using the plugins would be the best approach or you can use some web service with Insert From URL to send email, bypassing your local email client.
When you say "on the server" you don't mean with PSOS or a scheduled server script, do you? The open url script step isn't supported on FMS.