Hi,
We have just installed a Sophos XG firewall, replacing a Fortigate. Everything is working well except for the user experience in Outlook. Users complain that emails take a long time to open. I have seen this myself, but its not consistent - sometimes emails open immediately, other times you are waiting for 5+ seconds for the email to appear on the screen. And in fact I can be on one session on the same server with my email working fine while another user in another session on the same server can be waiting a long time for email.
The user environment is RDP servers, Office 365, and Outlook in "online mode" (not cached). Changing users to "cached mode" obviously works around the issue, and I plan to do that once I fix this problem, but this is a regression - it was working fine under Fortigate - so I don't want to hide the problem by implementing "cached mode".
We are not using SSL inspection, and I have disabled ATP and all HTTP scanning in a test rule, and the problem still persists. There are no IPS or DoS rules enabled. As far as I can tell, for the affected users the Sophos XG is acting as nothing more than a proxy router.
There are two WAN connections with load balancing between them, but even after forcing all traffic over one connection with a specific rule, the problem still persists.
The WAN connections are under 5% capacity most of the time so it's not network congestion.
There are no errors on the Ethernet interfaces.
Any suggestions?
thanks
James
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