How to release Outlook MailItem correct?

Question

I just can't release my Outlook MailItems. After opening 200 Mails the Exchange Sever returns the maximum open Emails is reached.

I'm remove my UserProperty from all selected Mail.

My Code:

foreach (var selection in Globals.ThisAddIn.Application.ActiveExplorer().Selection)
{
 if (selection is MailItem)
 {
  MailItem mi = (MailItem)selection;
  UserProperty up = mi.UserProperties.Find("MyProp");
  if (up != null)
  {
   up.Delete();
   //##################################
   // I also tried :
   //----------------------------------
   //    Marshal.ReleaseComObject(up);
   //    up = null;
   //----------------------------------
  }

  mi.Save();

  //##################################
  // I also tried :
  //----------------------------------
  //     mi.Close(OlInspectorClose.olDiscard);
  //----------------------------------


  // I don't know if this loop is necessary, but I have found it somewhere on the web
  while (Marshal.ReleaseComObject(mi) > 0);
  mi = null;

  //##################################
  // I also tried :
  //----------------------------------
  //    GC.Collect();
  //    GC.WaitForPendingFinalizers();
  //----------------------------------
 }
}

Any idea what's wrong?

Answer 1

You can try this: Instead of defining a new MailItem everytime within the For loop, can you define mi outside the For loop or even in your class level, and reuse it for each mailitems? e.g:

MailItem mi;
foreach (var selection in Globals.ThisAddIn.Application.ActiveExplorer().Selection)
{
 if (selection is MailItem)
 {   
   mi= (MailItem)selection;
   // your other code...
 }
 }
mi=null;
GC.Collect();
GC.WaitForPendingFinalizers();

EDIT:

Try to create local variable for each references e.g:

Outlook.Explorer myExplorer=Application.ActiveExplorer(); 
Outlook.Selection mySelection=myexplorer.Selection; 
foreach (var selection in mySelection)
{
}
myExplorer=null;
mySelection=null;
//....

EDIT-2:

IF you are using Outlook 2010 check this: Outlook 2010 addin selection not clearing