We have an Exchange Server 2010 V 14.01.438 running on Window Server 2008 R2 Enterprise, which stopped receiving incoming emails about three hours ago, however everything we checked appears to be in order.

Items we checked so far:

  • Internal emails are working fine
  • Outgoing emails are working, a 10-14 second delay more than usual is felt
  • Nothing in incoming queues on management console
  • New incoming messages do not appear be go through the ORF (so we thought perhaps an incoming port block)
  • SMTP test from MXToolBox passed
  • Server is not blacklisted (MXToolBox)
  • Telnet to server's port 25 works fine, also from outside the network
  • Senders (we used gmail for testing) are not receiving any error messages
  • We tried restarting the information store service and the server itself
  • Additional info: No update / work was done on the server in the past week. The drive which is running Exchange has 8.5GB free. Server does not appear to be under any loads

Any suggestions ?

  • Are you certain that your MX record is correct and resolving to the A record of the host properly? – Evan Anderson Jul 9 '14 at 14:05
  • Hi @EvanAnderson and thank you for your reply. Yes we are sure, we checked this using the mxtoolbox tools. The address was correctly resolved and pointed to the correct server. – Bdevelle Jul 9 '14 at 14:15
  • It'd be useful if you could give me an address at the domain to test sending to, and then I can see what appears in the mail logs. – Phil Jul 9 '14 at 14:20
  • Also, 8.5GB free out of what? If it's a large volume, that might be low enough to stop Exchange functioning normally on it's default thresholds - see technet.microsoft.com/en-us/library/dd146168.aspx – Phil Jul 9 '14 at 14:22
  • 1
    umm... how are you clearing out the log files? The proper way would be to actually run the backup. Worse case would be to turn on circular logging. Under NO circumstance should you just be deleting log files manually. – Rex Jul 9 '14 at 16:40

Exchange server enters back pressure mode and refuses external mail when available disk space drops to around 2%.

If there is no obvious reason for your server to be running out of space, check that your backups are running properly as otherwise your exchange transaction logs will eventually fill your disk.

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