Unable to receive mail from external domains

Our client  running their own web and mail servers. hosted with private IP , connected after Fortigate Firewall. Mails are working well. All of sudden past one week we are not able to receive mail from external domains. We tested the following
1. Send and receive locally ---------------------------------------- Working
2.Sending mails to external domains like yahoo, gmail---------- working
3.Receving mails from External domains like yahoo, gmail------FAILED
4.Telnet the port 25 and 110 both with public and private IP---Working
5. Checked the MX record pointing to Public ip at whois
    and private IP in the Firewall-------------------------------------Working
6. CHecked the NODE32 AV@ server for any blocked mails-- No mails blocked
7. DIsabled Microsoft Antispam update in the services of SERVER
8. Checked the Hub and Transport Roles of SERVER.
Can anyone help with solution
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Beyond Next SolutionsSolutions ArchitectCommented:
Is the problem specifically with some domains (like Yahoo, Gmail) or with all external domains sending inbound? First thing to try is the inbound SMTP test at the bottom of this page:
Try to disable all options under "anti-spam" tab in EMC.
EMC - org config - hub transport- anti spam.
dinagaran2000managerAuthor Commented:
Sorry Team,
           Because of power issue , total OS itself corrupted.

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dinagaran2000managerAuthor Commented:
Since server itself corrupted. Planning to install new server.
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