Hi,
I've sent an email to Idnet help but I thought I'd ask here as well. For the 24 last hours email forwarding has not worked from my domain name e-mail address to my Idnet email address. As a test I changed the email address in 123reg where emails get forwarded to and messages I expecting to have received arrived perfectly well. However, when I switched my forwarding email address back to my Idnet email address it fails to work again. I'm nowhere near out of space on my Idnet webmail account.
I had a similar (ish) problem recently, in that one of my IDNet email accounts suddenly wouldn't receive mail from a particular sender. I set up a whitelist filter on the IDNet account and that seemed to do the trick (it takes about 15 minutes to come into effect). Maybe you could try setting up a whitelist filter for your forwarding email address?
What I meant to write was that emails sent to my domain e-mail address are not being redirected to my Idnet address.
Email forwarding conflicts with anti-spam measures, especially SPF rules that say "this email address can't come from this server".
Whenever I experience a problem my first course of action is to reboot. It cures 90% of ailments. 8-)