cPanel and Outlook Autodiscover

If you have a cPanel customer who also has an SSL certificate for their website, you may find that Outlook Autodiscover does not work properly (especially with older versions) as cPanel matches /Autodiscover/Autodiscover.xml and gives the client IMAP/SMTP settings instead of giving a 404 and letting it move on. You may even find that your requests are redirected to cpanelmaildiscovery.cpanel.net/autodiscover/autodiscover.xml which is obviously not desired. In this case, there is a quick fix, though it's really more of a hack. This assumes you're using Apache.

1. Edit /etc/httpd/conf/httpd.conf
2. Search for autodiscover, you should find a ScriptAlias line referencing it
3. Comment this line out or remove it completely
4. Restart apache (service httpd graceful)
5. Edit /usr/local/cpanel/APACHE_CONFIG and find the same line and remove it
6. At the top of your httpd.conf you should also have details on how to make cPanel retain the settings, i ran /usr/local/cpanel/bin/apache_conf_distiller --update to save the changes to the template.

Obviously a cPanel update could potentially overwrite these changes, but as far as i could tell this is the only way to get it to actually behave correctly.

Exchange Autodiscover after an On-Premise to Office 365 Migration

If for whatever reason you decided to do a cutover or similar migration from On-Premise Exchange to Office 365, you may find that Autodiscover can be a little sticky. The issue that I ran into is that for this environment the computers are domain joined, but we cannot immediately uninstall Exchange to remove the organization info from Active Directory. Due to this, when Outlook starts up and searches for Autodiscover, it will search for a SCP (Service Connection Point) in Active Directory, which will still be there and pointing to the wrong spot. Best case scenario this can make it take longer to start up, worst case it can end up either pointing to the wrong spot or certificate errors. The solution, though it's a bit of a hack, is to just change the connection point. I did this with ADSI Edit, note that I consider this a temporary workaround and not a permanent fix. Once you uninstall Exchange then all of this is removed from AD.

1. Open adsiedit.msc (typically from a Domain Controller)
2. Connect to the Configuration context
3. Navigate to Configuration > Services > Microsoft Exchange > (OrgName) > Administrative Groups > (Your Administrative Group Name) > Servers > (Server Name) > Protocols > Autodiscover
   
4. Edit the entry for your server and scroll down to ServiceBindingInformation
   
5. Adjust the value to reference the proper URL for your Office 365 environment. If you don't know, you can use the Autodiscover test in testconnectivity.microsoft.com to verify what your URL should be.
6. Outlook should detect it properly now, you can also verify by using the connectivity tester built into Outlook by Ctrl+Clicking the Outlook system tray icon and selecting Test E-Mail AutoConfiguration

Windows Server Unable to Make Outbound TCP Connections

Ran into an issue with a customer server where various things were just not working. A reboot always fixed it, but it had to be done every few days which was not acceptable. The types of errors being received were things like "no logon servers are available" or being unable to open any Active Directory tools. DNS and network shares were working fine, i could RDP in without issues, restarting various services did not help, ICMP/UDP were fine. I attempted to telnet out but any outgoing connection was immediately aborted, wireshark did not see the connection attempt, all firewalls were off.

I ended up putting PuTTY on the server and tried to telnet from there, and received a more specific "no buffer space available" error. Searching for that, i determined it was a Winsock error related to not enough free handles being available. With that knowledge, i opened the task manager and added the Handles column and sorted. There it was, an HP Plotter utility service with 6000+ open handles. I killed the process and everything immediately went back to normal.