Hi @Anonymous,
I am not sure if the search query parameter supports the le operator.
However, as a workaround you could use the Graph API instead with a filter query parameter. You can for example use that in a Send an HTTP request action from the Office 365 Groups connector..
Below is an example of that approach.
Btw, I would use a ge instead of an le because you everything from the last 30 days, correct? In this example I am only retrieving the receivedDateTime and subject of the individual e-mails. Remove that &select= part if you want to retrieve all properties 😁
https://graph.microsoft.com/v1.0/me/messages/?$filter=receivedDateTime gt @{addDays(utcNow(), -30, 'yyyy-MM-ddTHH:mm:ssZ')}&$select=receivedDateTime,subject
