Issue with remote download reports (Report Widget)

Hi!
I have a problem when I try to download the reports remotely from the Report Widget .When I do it from my local network I have no problem because the link at the e-mail arrives with my local IP, but when I try it remotely, the only way is writting my ddns address (I do not have public IP in my house). Is there any way to modify my local server to send the email with my DDNS address?
Sorry about my spanglish.
Thanks
Pancho