OZG-5243 add mail list to component

alfa-client/apps/alfa-e2e/src/page-objects/postfach-mail.component.po.ts

@@ -29,6 +29,7 @@ export class PostfachMailPage {
   private readonly breadcrump: string = 'postfach-breadcrump';
   private readonly root: string = 'postfach-mail-list';
   private readonly downloadButton: string = 'postfach-pdf-export-button';
+  private readonly mailText: string = 'postfach-outgoing-nachricht';
 
   private readonly subnavigation: PostfachMailSubnavigation = new PostfachMailSubnavigation();
 
@@ -51,4 +52,8 @@ export class PostfachMailPage {
   getDownloadButton() {
     return cy.getTestElement(this.downloadButton);
   }
+
+  getMailText() {
+    return cy.getTestElement(this.mailText);
+  }
 }