Exchange 2010 external attachments are blocked over 500 kb

Hi,
We are running a new exchange 2010 SP2 installation. Sending attachments in big size is no problem within the domain, but every external mail with an attachment over 500 kb is just lost. No error message to the sender, no message in queue, just nothing. Tried every size settings in the hub transport, receive connectors and the mailboxes. It's just a simple network with a Zyxel USG20 firewall with deactivated content filters. Tried also to deactivate the firewall and antivirus. Any idea?
Thanks!
dirkmeinlAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

dirkmeinlAuthor Commented:
Problem solved! Replacing the Zyxel USG20 made us happy.
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Exchange

From novice to tech pro — start learning today.