for the past one week we have not been able to recieve nor send mail within/outside our network. from the event log if find the error message below. i have check our firewall for the closed ports and they are ok, i also check the send connection in the edge server and is ok. so can anybody help pls

Check the ADAM service is running under which account

By default it should be network if its running in a different account check if the password of that account is expired

Hi,

According to the error message, it indicate that the Microsoft Exchange EdgeSync service did not validate the future replication account credentials that are required to replicate Active Directory data to the Edge Transport server.

It might be caused by DNS, certificate and network connectivity as error description mentioned. We need to check them one by one.
Firstly, confirm network connectivity and DNS:
1. Check port 50636 is open between the MBX and Edge. Do telnet tests and confirm and check with network team if firewall is allowing this.
2. In the host of the Edge, put in an entry so that is can resolve the MBX FQDN.
3. Check DNS resolution from both the MBX and Edge, make sure they can resolve each other.

Secondly, check the services on MBX and Edge server:
1. Restart the following services on MBX Server
   Microsoft Exchange EdgeSync
   Microsoft Exchange Transport
2. Restart the following services on Edge Server
   Microsoft Exchange ADAM
   Microsoft Exchange Credential service
   Microsoft exchange Transport

Lastly, use get-exchangecertificate | FL to confirm if the certificate meet the FQDN of Edge Server, if it has been enabled for SMTP service.  If not, then it could be the certificate related issue. You can refer to the Felix post in similar thread to solve the problem: https://social.technet.microsoft.com/Forums/en-US/4349b146-ad6e-44a2-9d3e-52158eee8a5d/edgesync-errors?forum=exchangesvrsecuremessaginglega