Deskpro looks at the Email headers to determine who the User is. Some Email server configurations do not send the correct User information in the From: header. This can happen if you are automatically forwarding Emails or using distribution lists.

Sometimes, the correct User address is retained in the Reply-To or X-Original-From header, even if From: is wrong.

You can set the order that Deskpro looks at headers in Channels > Emails > Settings, in the Email Settings section drag and drop the headers into the order you want, using the dots on the left hand side, putting the most reliable header at the top.