Import / migrate Gmail email messages; How to avoid duplicates from Sent folder?

Import / migrate Gmail email messages; How to avoid duplicates from Sent folder?

I have Gmail setup so that every conversation (group of email messages) is assigned ONE and ONLY ONE label.  This helps me use the Apple Mail app as a normal IMAP client with Gmail, and avoid duplicate messages across folders.  Of course, any email message that I have sent is available in the Sent folder (both in Gmail and Apple Mail).

However, when I migrate Gmail email messages to Zoho Professional, Zoho duplicates all messages in the Sent folder.  In other words, it sees this conversation, assigned to the label "Work", with four messages:

-Doug email to Bob
-Bob reply to Doug
-Doug reply to Bob
-Bob reply to Doug

What Zoho does is create individual email messages in both the Work folder and the Sent folder, since I sent the first and third emails.  So if I search for "Bob", I see duplicate messages, showing up in Work and Sent. Why Zoho doesn't automatically handle the Sent folder like Apple Mail, I dunno.

In any case, there must be something I'm missing, since I can't imagine everyone migrating Gmail to Zoho either has thousands of dupes or doesn't import their Sent folder.

Any ideas?  Thanks!