This the PopulateMessage function that is being called in the loop.  I also tried not to reference any images, or not to populate Tag property, but result was only different by few hunder kB.

    Private Sub PopulateMessage(ByVal item As Infragistics.Win.UltraWinListView.UltraListViewItem, ByVal Message As SCE.SCEInterfaces.IMessage)
        item.Tag = Message
        If folderBar.ActiveItem IsNot Nothing Then
            Select folderBar.ActiveItem.Key
                Case "Sent", "Draft", "Ready To Send", "Send Errors"
                    item.SubItems("From").Value = Message.SendTo
                Case Else
                    item.SubItems("From").Value = Message.SenderEmail
            End Select
        End If
        item.SubItems("Subject").Value = Message.Subject
        item.SubItems("Received").Value = Message.CreateDate
        If Message.Folder IsNot Nothing Then
            item.SubItems("Folder").Value = Message.Folder.Name
        Else
            item.SubItems("Folder").Value = ""
        End If
        If Message.Attachments.Count > 0 Then
            item.SubItems("Attachment").Appearance.Image = My.Resources.attach
        Else
            item.SubItems("Attachment").Appearance.Image = Nothing
        End If
        Select Case Message.HighlightColor
            Case SCE.eMailMessageColor.None
                item.SubItems("Important").Appearance.Image = My.Resources.bullet_white
            Case SCE.eMailMessageColor.Blue
                item.SubItems("Important").Appearance.Image = My.Resources.outlook_flag_blue
            Case SCE.eMailMessageColor.Green
                item.SubItems("Important").Appearance.Image = My.Resources.outlook_flag_green
            Case SCE.eMailMessageColor.Orange
                item.SubItems("Important").Appearance.Image = My.Resources.outlook_flag_orange
            Case SCE.eMailMessageColor.Red
                item.SubItems("Important").Appearance.Image = My.Resources.outlook_flag_red
        End Select
        If Message.SendDate > #1/1/2000# Then
            item.SubItems("Sent").Value = Message.SendDate
        Else
            item.SubItems("Sent").Value = ""
        End If
        If Message.LastReadDate > #1/1/2000# Then
            item.SubItems("Last Read").Value = CDate(Message.LastReadDate.ToShortDateString)
        Else
            item.SubItems("Last Read").Value = Nothing
        End If

        If Message.Type = SCE.eMailMessageType.Incoming And Message.LastReadDate < #1/1/2000# Then
            item.Appearance.FontData.Bold = Infragistics.Win.DefaultableBoolean.True
            item.Appearance.Image = My.Resources.mail_new
        Else
            item.Appearance.FontData.Bold = Infragistics.Win.DefaultableBoolean.False
            Select Case True
                Case Message.IsDraft
                    item.Appearance.Image = My.Resources.mail_draft
                Case Message.ForwardedMessage IsNot Nothing
                    item.Appearance.Image = My.Resources.mail_forward
                Case Message.RepliedMessage IsNot Nothing
                    item.Appearance.Image = My.Resources.mail_reply
                Case Else
                    item.Appearance.Image = My.Resources.mail
            End Select
        End If
    End Sub

yes .. that worked .. created predifned apperances and RAM usage went down to 100mb

Hello ,

Thank you for the provided code snippet . As far as I can see from your PopulateMessage function you are adding a lot of images to your SubItems and I think that this is the reason for a large amount of ram, because when you add an image, font and etc. to the default appearance object, the component should create a new instance of appearance object. When you have 2800 items, it is about 2800*7 (because you are setting an image on almost each sub item) appearance objects, loaded in the ram, and each of them contains an image (which is ram consuming resource). So my suggestion is to create several appearance object, which you could reuse them. Please implement this suggestion and let me know for the results.

I am waiting for your feedback.

Also, if I clear items and try to repopulate,  ram usage almost doubles.  when theoretically garbage collection should release memory from cleared items, and reuse for new items.