Vb.net Outlook选择已发送邮件文件夹中的第一个项目getfirst上周的项目，而不是第一个项目

Dim outlookApp As New Outlook.Application
Dim outlookNamespace As Outlook.NameSpace = outlookApp.GetNamespace("MAPI")
outlookApp.Session.Logon()

Dim sentFolder As Outlook.MAPIFolder = outlookNamespace.GetDefaultFolder(Outlook.OlDefaultFolders.olFolderSentMail)

Dim items As Outlook.Items = sentFolder.Items
items.Sort("[ReceivedTime]", False)

Dim lastWeekStart As Date = Date.Today.AddDays(-Date.Today.DayOfWeek - 6)
Dim lastWeekEnd As Date = Date.Today.AddDays(-Date.Today.DayOfWeek)

Dim filter As String = "[ReceivedTime] >= '" & lastWeekStart.ToString("yyyy-MM-dd HH:mm") & "' And [ReceivedTime] <= '" & lastWeekEnd.ToString("yyyy-MM-dd HH:mm") & "'"
Dim lastWeekItem As Outlook.MailItem = items.Find(filter)

If lastWeekItem IsNot Nothing Then
    Dim subject As String = lastWeekItem.Subject
    Dim sender As String = lastWeekItem.SenderName
    ' 其他操作...
End If