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bmerri19
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Joined 5 years ago
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Not receiving emails from O365/Outlook.com companies with Barracuda email security
Hello, Have an odd email delivery issue, which was working up until about 5/27. We are no longer receiving emails from companies using O365/Outlook.com and Barracuda email security it appears (based on past working headers). Our internal org has Exchange 2016 on-prem behind SonicWall firewall/anti-spam. The working headers showed usually 8-9 hops, before delivering the email. Now we are only seeing the first two hops from the senders orgs, typically just the outlook.com servers. The senders are getting NDR's with this error: Remote Server returned '550 5.4.300 Message expired -> 421 temporary failure for one or more recipients (*****.**********@*********.org:451Proxy timed out)' Remote Server returned '550 5.4.300 Message expired -> 451 Proxy timed out' Not sure where the proxy in question resides. We are not seeing emails reaching our firewall, or Exchange 2016 SMTP receive logs. We've tested both orgs inbound/outbound SMTP for O365 and Exchange, via Microsoft Remote Connectivity Analyzer. Seems like a sender side issue, but they are reporting no issues from O365/Barracuda. Any thoughts? Thanks.12KViews0likes9Comments
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