Some clients will not be able to configure their emails with Outlook Express which installed win Windows 7. The reason is your windows version is using the old TLS encryption method and you have to update your windows. Refer to this document and follow all steps.
https://manage.accuwebhosting.com/knowledgebase/3008/How-do-I-enable-TLS-12-on-Windows-7.html
Anyway if you can use the Thunderbird email client, it will simply connect to your mail server.
