Haven't tested.. but something like this

HCL Notes/Domino 8.5 Forum (includes Notes Traveler)

Subject:

I created this in the catalog.nsf. An agent that I would run manually and the targe is set to none

Dim session As New NotesSession
Dim db As NotesDatabase
Dim mailDb As New NotesDatabase("","")
Dim mailDBcollection As NotesDocumentCollection
Dim sFormula As String
Dim mailDBEntry As NotesDocument
Dim mailCollection As NotesDocumentCollection
Dim emailDoc As NotesDocument
Dim reportDoc As NotesDocument
Dim rtitem As NotesRichtextitem
Set db = session.currentdatabase

sFormula = |form = ""Notefile"" & @Contains(Pathname;"mail\")|
Set mailDBCollection = db.search(sFormula,Nothing,0)
If mailDBCollection.count = 0 Then
Exit sub
End If
Set reportDoc = db.Createdocument()
Set rtitem = New NotesRichTextItem(reportDoc,"Body")
Set mailDBEntry = mailDBCollection.Getfirstdocument()
Do Until mailDBEntry Is Nothing
If mailDb.open(db.server,mailDBEntry.pathname(0)) Then
sformula = |@AttachmentLengths > 100000000|
Set mailCollection = mailDb.search(sformula,Nothing,0)
If mailCollection.count = 0 Then
Else
Call rtitem.appendtext(mailDBEntry.pathName(0) & " contains the following docs with attachments > 1mb:")
Call rtitem.Addnewline(1)
Set emailDoc = mailCollection.getfirstdocument
Do Until emailDoc Is Nothing
Call rtitem.appendText(emailDoc.subject(0))
Call rtitem.Appenddoclink(emailDoc,"Mail document")
Call rtitem.Addnewline(1)
Set emailDoc = mailCollection.getnextdocument(emailDoc)
Loop

End If
End If
Call rtitem.Addnewline(2)
Set mailDbEntry = mailDBCollection.Getnextdocument(mailDbEntry)
Loop
With reportDoc
.sendTo = "Put your username"
.subject = "Report of emails containing attachments > 1mb"
End With
Call reportDoc.send(False,False)

Feedback response number WEBBA6SQCE created by ~Hal Quetlu on 02/03/2016