Making unambiguous concatenate when retrieving info for email - excel

Question

The aim is to check individual worksheets for a list of dates in a range, and then send an email listing these dates to an email address located in the sheet.
The current code concatenates the dates in the current sheet as well as the dates on the previous sheet, instead of just the dates found on this sheet.
I'm struggling to make it uni-vocal, tried putting "ws." before each aCell instruction but get compile error.
Sub Mail_Outlook()
Dim ws As Worksheet
Dim wsName As Variant
Dim OutApp As Object
Dim OutMail As Object
Dim cell As Range
Dim strbody As String
Dim string1 As String
Dim aCell As Range
Dim i As Integer
i = 0
For Each wsName In Array("sheet1", "sheet2", "sheet3")
Set ws = Worksheets(wsName)
'retrieve all missing dates
For Each aCell In ws.Range("Aa1:Aa1000")
If aCell.Value <> "" Then
i = i + 1
If i <> 1 Then
string1 = string1 & ", " & aCell.Value
Else
string1 = aCell.Value
End If
End If
Next
'send email
Set OutApp = CreateObject("Outlook.Application")
Set OutMail = OutApp.CreateItem(0)
strbody = "Good day " & ws.Range("E3").Cells & vbNewLine & vbNewLine & _
"" & vbNewLine & vbNewLine & _
"" & vbNewLine & vbNewLine & _
string1 & vbNewLine & vbNewLine & vbNewLine & vbNewLine & _
"(This is an automated message)" & vbNewLine & vbNewLine & _
"Best regards" & vbNewLine & vbNewLine & _
On Error Resume Next
With OutMail
.To = ws.Range("E5").Text
.CC = ""
.BCC = ""
.Subject = ""
.Body = strbody
'You can add a file like this
'.Attachments.Add ("C:\test.txt")
.Display 'or use .Send
End With
On Error GoTo 0
Set OutMail = Nothing
Set OutApp = Nothing
Next
End Sub
From the OP's comments:
code as is produces no errors, but e.g. the second email contains the string for the first sheet and second sheet, rather than just the second sheet.

Answer 1

Zero the string before going into the second iteration of the loop.
For Each wsName In Array("sheet1", "sheet2", "sheet3")
Set ws = Worksheets(wsName)
string1 = vbNullString 'reset string1 to a zero-length string for each ws
'retrieve all missing dates
For Each aCell In ws.Range("Aa1:Aa1000")
'all the rest of the concatenation code
next aCell
'all the rest of the email code
Next wsName