Question : 550 Requested action not taken: mailbox unavailable - Exchange Server

Hi Experts

We are running Windows 2003 64Bit and Exchange 2007 server. Everything is working fine inside our company but we got a remote user using Outlook client 2003 that is getting error below when he try to send emails outside our company (he can send emails out to exchange users):

550 Requested action not taken: mailbox unavailable

I try same thing using Outlook client 2007 and everything works fine, thus our user can send emails out to exchange and outside users.

We have a watchguard firewall protecting our network but it is allowing incoming email on port 25 and as I told you before everyone inside our organization can send and receive emails without any problem

Any help with this issue will be greatly appreciated.

Regards,

Jaime

Answer : 550 Requested action not taken: mailbox unavailable - Exchange Server

Hello all,

Problem we  were having was solved addding a true certificate from Digicert. Now we can get Outlook 2003 clients working on any version Windows OS (Prof., Home Edition, etc).

Regards,

Jaime