For those who’ve been asking how to migrate Pegasus Mail to Office 365 without messing up mailbox integrity — it’s definitely possible, but manual conversion won’t guarantee structure preservation. Pegasus stores emails in unconventional formats and doesn’t naturally align with Microsoft 365’s authentication or mailbox structure. I ended up trying the SysInfo IMAP Backup Tool, which directly moves IMAP mailboxes to Office 365. The standout functionality for my use case was its Duplicate Email Removal. With Pegasus, users often have multiple local folders and mirrored backups, so duplicates can inflate mailbox sizes quickly. This feature saved space and kept the final destination clean. Performance-wise, the migration was fast, and it didn’t break header information or attachments. For anyone modernizing old local email clients into the cloud, tools like this make the jump far less risky compared to multi-step manual conversions.

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