Outlook event function triggers multiple times when used on shared mailbox - C# - outlook

Question

I've function which checks every new coming email inbox and if it is reply, it would move it to "Reply" folder.
It runs on shared mailbox in multiple people's PC. The problem is, it moves the email file but creates multiple copies of the same email into "Reply" folder. How can I fix it?
Here is my code, any help will be appreciated.
Thank you.
Outlook.NameSpace outlookNameSpace;
Outlook.MAPIFolder inbox;
private Outlook.Items items;
private void ThisAddIn_Startup(object sender, System.EventArgs e)
{
Outlook.NameSpace ns = Globals.ThisAddIn.Application.Session;
Outlook.MAPIFolder inbox = ns.GetDefaultFolder(Outlook.OlDefaultFolders.olFolderInbox);
outlookNameSpace = this.Application.GetNamespace("MAPI");
string recipientName = "abc#abcd.com";
Outlook.Recipient recip = outlookNameSpace.CreateRecipient(recipientName);
recip.Resolve();
if (recip.Resolved)
{
inbox = outlookNameSpace.GetSharedDefaultFolder(recip, Outlook.OlDefaultFolders.olFolderInbox);
items = inbox.Items;
items.ItemAdd += new Outlook.ItemsEvents_ItemAddEventHandler(items_ItemAdd);
}
}
void items_ItemAdd(object Item)
{
if (Item != null)
{
Outlook.MailItem mail = Item as Outlook.MailItem;
if (mail.MessageClass == "IPM.Note")
{
try
{
Outlook.Application app = Globals.ThisAddIn.Application;
if (Item is Outlook.MailItem)
{
if (mailItem.ConversationIndex.Length >= 64)
{
Outlook.Folder nonInbox = folder.Parent as Outlook.Folder;
string FolderName = "Reply";
Outlook.MAPIFolder DestFolder = null;
try
{
DestFolder = nonInbox.Folders[FolderName];
}
catch
{
}
try
{
mailItem.Move(DestFolder);
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
}
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
}
}

Answer 1

The way I dealt with it is when our user reply to email, it will save custom user property along with original email from customer. User property is our user's name. When they get reply from customer, add-in checks if current user is same as user property saved in original email, if they are same; then add-in will move the email to folder. Like this, condition on every reply will be true only once.