Maintaining complete email data when trying to import EML files to Office 365 without losing attachments is a frequent concern, especially when the source files come from multiple email clients with varying attachment structures. The SysInfo EML to Office 365 Migration Tool handles both message content and associated attachments during the migration, ensuring nothing is dropped or separated from the original email at the destination Office 365 mailbox. The preview feature adds a useful verification layer—before initiating the migration, the tool displays each EML file in a tree structure showing From, Subject, Date, Message Content, and Attachments, allowing confirmation that attachment data is intact prior to transfer. For cases where attachment transfer is not required, a built-in toggle allows migrating or backing up emails without attachments, giving flexibility depending on the specific migration requirement. The tool supports EML files created in Thunderbird, Apple Mail, Outlook Express, Windows Live Mail, and other email clients without compatibility issues. It runs on Windows 11, 10, 8.1, 8, 7, XP, and Vista, with a free version available that converts up to 50 emails per folder at no cost.