If you need Outlook integration, use verified extensions from the Chrome Web Store or Microsoft Marketplace . Did you download this file from a specific website , or
If your goal is to verify if an email list is valid or to check your own inbox, use these trusted services instead: Mail Access Checker.exe
Software with this name is commonly found in "dark web" or grey-market forums as a "combo checker" used to test stolen email/password credentials. If you need Outlook integration, use verified extensions
Mail Checker for Outlook™ | Save email to PDF, TXT or HTML Legitimate Alternatives Overview
These programs may contain backdoors designed to steal the very credentials you are testing or to use your machine as part of a botnet. Legitimate Alternatives
Overview. Mail Checker for Outlook™ lets you receive emails, save as PDF, TXT, or HTML, reply, and get notifications. Chrome Web Store Email Viewer Software - Microsoft Marketplace