We have an interesting situation.

One of the domains we house has multiple users all behind the same office IP address.

Since moving them over to our SM install, we're seeing hundreds of thousands of hits per day in our log files to the webmail server, and thousands of entries in our administration.log file that say the following:

[AUTHENTICATION SERVICE] 1 guidHash was null

We have other domains that are under the same circumstances with even more user accounts behind one IP and their traffic usage is just as heavy, but they don't generate these errors, and they don't seem to beat on the webserver with millions of hits to:

(Screenshot to log results from IIS): https://dedicate-it.net/log-img/webmail-smash.png

We see these from some other users, but only one or two a day - but this particular domain there are thousands - and they're constant.  

On a sidenote, we have even had to put in a redirect that catches old MailEnable webmail URLs and automatically redirects to the SmarterMail root login page - as that was another issue that was just beating on the web server because of bad user bookmarks.

SM details:

Info	SmarterMail Enterprise 100.0.8594.33598 (Jul 13, 2023)
Info	Hosting Process: w3wp
Info	Pipeline Mode: Integrated
Passed	Microsoft.Net Framework Version: 4.8 or later