Clarify preview export button label

mail_exporter.py

@@ -71,7 +71,7 @@ Preview and filters
 Export modes
 - Create zip builds a ZIP archive.
 - Create folders on file system writes the export as folders and files.
-- Export preview exports only the emails currently visible in the filtered preview.
+- Export visible emails exports only the emails currently visible in the filtered preview.
 
 Notes
 - Classic Outlook for Windows must already be installed and configured on this PC.
@@ -1745,7 +1745,7 @@ class OutlookExporterApp(ctk.CTk):
         )
         self.btn_export_preview = ctk.CTkButton(
             preview_actions,
-            text="Export preview",
+            text="Export visible emails",
             width=150,
             command=self.export_preview_subset,
             state="disabled",
@@ -2291,7 +2291,7 @@ class OutlookExporterApp(ctk.CTk):
         labels = {
             EXPORT_MODE_ALL: "Export all",
             EXPORT_MODE_WITH_ATTACHMENTS: "Export emails with attachments only",
-            EXPORT_MODE_FILTER: "Export preview",
+            EXPORT_MODE_FILTER: "Export visible emails",
         }
         return labels.get(export_mode, export_mode)