bij microsoft vind ik:
"Error 0x80072726
An error 0x80072726 might be due to third-party firewall or related security software, such as anti-virus software. While we don't recommend disabling anti-virus or firewall software, you can visit the software manufacturer's website to see if they have workaround steps or you can temporarily disable the software to see if that fixes the issue. If so, work with the software manufacturer's technical support to find a way to access your email without disabling their software.
Warning: If you disable your anti-virus software, don't open any email attachments or click any links in messages from people you don't know."