VBA Application-defined error outlook connection - excel

Question

I have the following code and keep having the error "application-defined or object-defined error" and cannot understand why. The tool Microsoft Office 16.0 Object library is activated, I am confident that the error is liked with the line Set outlookMail = outlookApp.CreateItem(0). For sure I am missing something in the connection with outlook.
Sub send_emails()
Dim outlookApp As Object
Dim outlookMail As Object
Dim cell As Range
Dim lastRow As Long
' Create Outlook object
Set outlookApp = CreateObject("Outlook.Application")
' Determine the last row in the worksheet
lastRow = ActiveSheet.Cells(Rows.Count, "A").End(xlUp).Row
' Loop through each cell in column D
For Each cell In Range("D2:D" & lastRow)
' Check if the date in the cell is 15 days from today
If cell.Value = Date + 15 Then
' Retrieve the corresponding email address, name, and surname
Email = cell.Offset(0, 2).Value
Name = cell.Offset(0, 1).Value
surname = cell.Offset(0, -1).Value
' Create a new email
Set outlookMail = outlookApp.CreateItem(0)
' Set the recipient, subject, and body of the email
outlookMail.To = Email
outlookMail.Subject = "Reminder"
outlookMail.Body = "Dear " & Name & " " & surname & ", this is a reminder that your event is coming up in 15 days. Please make sure to prepare accordingly."
' Set the sender and send the email
outlookMail.SendUsingAccount = outlookApp.Session.Accounts.Item("YOUR EMAIL ADDRESS")
outlookMail.Send
' If the email was sent successfully, color the cell in column E green
cell.Offset(0, 1).Interior.Color = vbGreen
End If
Next cell
' Clean up
Set outlookMail = Nothing
Set outlookApp = Nothing
End Sub

Answer 1

The tool Microsoft Office 16.0 Object library is activated
I suppose you have added a reference to the Outlook object model (a COM reference) in Excel VBA environment. In the code I see that the late-binding technology is used:
Dim outlookApp As Object
Dim outlookMail As Object
' Create Outlook object
Set outlookApp = CreateObject("Outlook.Application")
But at the same time you added a COM object reference for using the early-binding in the code. So, I'd suggest using the New operator and declare all Outlook objects in the code with specific types instead:
Dim outlookApp As Outlook.Application
Dim outlookMail As Outlook.MailItem
Set outlookApp = New Outlook.Application()
You can read more about early and late binding technologies in the Using early binding and late binding in Automation article.

Answer 2

Send Emails From Excel
Option Explicit
Private Enum eCols
ecSurName = 1 ' C
ecDate = 2 ' D
ecName = 3 ' E
ecEmail = 4 ' F
End Enum
Sub SendEmails()
Const MY_EMAIL As String = "YOUR EMAIL ADDRESS"
On Error GoTo ClearError
' Reference the worksheet.
If ActiveSheet Is Nothing Then Exit Sub ' no visible workbooks open
If Not TypeOf ActiveSheet Is Worksheet Then Exit Sub ' not a worksheet
Dim ws As Worksheet: Set ws = ActiveSheet
' Reference the range.
Dim LastRow As Long: LastRow = ws.Cells(ws.Rows.Count, "A").End(xlUp).Row
If LastRow < 2 Then Exit Sub ' no data
Dim rg As Range: Set rg = ws.Range("C2", ws.Cells(LastRow, "F"))
' Write the values from the range to an array.
Dim Data(): Data = rg.Value
' Write the matching rows to a collection.
Dim coll As Collection: Set coll = New Collection
Dim r As Long, rDate As Variant
For r = 1 To UBound(Data, 1)
rDate = Data(r, eCols.ecDate)
If IsDate(rDate) Then
If rDate = Date + 15 Then coll.Add r
End If
Next r
If coll.Count = 0 Then Exit Sub ' no matches
' Send the emails.
Dim olApp As Object: Set olApp = CreateObject("Outlook.Application")
Dim crg As Range, rItem, ErrNum As Long, emCount As Long
Dim olMail As Object, mEmail As String, mName As String, mSurName As String
For Each rItem In coll
mEmail = Data(rItem, eCols.ecEmail)
mName = Data(rItem, eCols.ecName)
mSurName = Data(rItem, eCols.ecSurName)
Set olMail = olApp.CreateItem(0)
With olMail
.To = mEmail
.Subject = "Reminder"
.Body = "Dear " & mName & " " & mSurName _
& ", this is a reminder that your event is coming up " _
& "in 15 days. Please make sure to prepare accordingly."
.SendUsingAccount = olApp.Session.Accounts.Item(MY_EMAIL)
On Error Resume Next ' suppress send error e.g. if invalid email
olMail.Send
ErrNum = Err.Number
On Error GoTo ClearError
End With
' Count and combine cells to be highlighted.
If ErrNum = 0 Then
emCount = emCount + 1
If crg Is Nothing Then
Set crg = rg.Cells(rItem, eCols.ecName)
Else
Set crg = Union(crg, rg.Cells(rItem, eCols.ecName))
End If
End If
Next rItem
ProcExit:
On Error Resume Next
' Highlight cells.
If Not crg Is Nothing Then crg.Interior.Color = vbGreen
' Clean up.
If Not olMail Is Nothing Then Set olMail = Nothing
If Not olApp Is Nothing Then Set olApp = Nothing
' Inform.
MsgBox IIf(emCount = 0, "No", emCount) & " email" _
& IIf(emCount = 1, "", "s") & " sent.", _
IIf(emCount = 0, vbExclamation, vbInformation)
On Error GoTo 0
Exit Sub
ClearError:
Debug.Print "Run-time error '" & Err.Number & "':" & Err.Description
Resume ProcExit
End Sub