Overview

A user is unable to login and access their mailbox from time to time, when they try to connect to the server via HTTP. However, logging in over HTTPS is working fine.

• Webmail shows the message "No internet connection".
• Security log on the mail server has the message: "HTTP connection from IP address <IP address> rejected: too many simultaneous connections (101 connections, limit 100)" though you are confident that the user does not have 100 connections to the server.
• You may have tried restarting the http service but that did not resolve the issue

Solution

This issue is probably being caused by something in the user's IP address making repeated connections to the server without closing them properly. Here is what you can do to resolve the issue:

• Long term: The only way to completely resolve this is to find the device/program making these connections and remove/re-add the account from it. This should resolve any configuration and corruption issues there.
• Short term: In the meanwhile, to allow the user to access the server again, you can simply restart the server as this will also reset the connections to the server, effectively zeroing the connection limit for all IP addresses.
  It is also recommended that you increase the server's limit to 600 (for both HTTP and HTTPS) as noted in Cannot Login Due to too Many Simultaneous Connections so that it will be much harder for the user to reach the limit again.