Numerous different IDs for the same Users

Hi everyone 👋

We are experiencing an issue with Numerous different IDs for the same users in Amplitude. In our workspace, we see that:

The same user appears with multiple IDs, causing duplicated profiles.
In many cases, Amplitude does not seem to detect the logged-in user emails properly.
This leads to duplication problems and makes it almost impossible to analyze user data correctly.

Has anyone faced this issue before?

What’s the best practice to avoid these inconsistencies between anonymous IDs, user IDs, and email properties?
Is there a recommended workflow to merge or unify IDs (for example, when a user first interacts anonymously and then logs in)?

Any guidance, examples or docs would be highly appreciated 🙏

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