(css) Fix printing of long mails

Fixes #3731

UI/WebServerResources/scss/core/print.scss

@@ -30,7 +30,8 @@
   // Horizontal flex layout must be ignored for element that could spawn multiple pages
   .view[layout="row"],
   section > div[layout="row"],
-  .msg-body > div[layout="row"] {
+  .msg-body > [layout="row"],
+  .mailer_mailcontent[layout="row"] {
     display: block !important;
     max-height: none !important;
     position: relative !important;