IMAP Search criteria

[Epitto]

Feature request or bug

nothing

If a bug, what did you expect to happen?

If a bug, what happened?

If a bug, list steps to reproduce bugs.

If a bug, did you do these steps?

[] Download and use the lastest stable version
[] See if the issue has already been reported
[] Debug

If a feature request, what do you want to be added or changed?

If a feature request, is this feature already in a pull request?

If a feature request, do you know anyone who can help?

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I want to use getMessagesByCriteria with the NOT operator and I can't figure out how to do it.
I tried with:
$criteria = "NOT TEXT 'string'"
$criteria = "TEXT NOT 'string'"
$criteria = "NOT 'string'"
...???

the error message is: Unknown search criterion ...
Do you have any suggestions?

Thanks