I get quite a few complaints from people who say their fonts are tiny (or huge) or the font used for the reply shrinks yet Microsoft Outlook shows they are using a normal size font (such as 10 or 12 pt). Outlook users with high resolutions screens may have a problem reading incoming emails.

This is caused by the Zoom setting.

Zoom Is On When Reading Mail

When your incoming email is zoomed, the easiest fix is to hold Ctrl as you roll the mouse wheel (this is the likely cause for many people).

Keyboarders can use the Ctrl and plus (+) or minus (-) keys to change the zoom level in increments or Ctrl and the zero (0) key to go to 100%. Note: these keyboard shortcuts do not work in Outlook 2013/2016.

You can also click the Zoom button in the ribbon and set it back to 100%.

Click the button in the ribbon to open the zoom dialog and select the desired zoom level.

Outlook 2010, 2013, and 2016 have a zoom slider in the main Outlook window status bar (on the right side). Use this slider to adjust the zoom in the reading pane.

If you prefer, you can click on the zoom % (100% in the screenshot) to open the zoom dialog.

Note that changing the zoom setting is not persistent for reading messages. To make the zoom level persistent, you need to use an add-in or a macro. A list of zoom tools is in the Tools Section and a macro is at the end.

When Composing Message, Zoom Is Always On

Many times, when you make the change to a message you are composing and send it, the next message you compose reverts to the goofy zoom setting. This is because making changes to a message then sending the message applies the changes to that message only. If you make the changes then close the message, it should apply the changes to all future messages.

When zoom is stuck on a value (usually a tiny font), you can reset it by changing the zoom level then closing, but not sending, the message. If you change the zoom level then send, the change applies only to the message you changed, not to future messages.

In Outlook 2016, the Zoom button is on the Format Text ribbon.

In Outlook 2010 and 2013, the Zoom button is on the Message tab when composing (or reading) a message.

1. Open a new message
2. Click the Zoom button on the ribbon
3. Change the zoom to the desired level
4. Close the message.
5. Click new message (or reply) and the zoom should be the desired level.

Zoom in either Open Messages or Reading Pane

While the zoom level is persistent when you change it in the compose mail window, it's not persistent when you change it for incoming messages.

This macro requires the use of Redemption (Developer Edition).

You need to set a reference to the Microsoft Word Object Library in the VBA's Editor. It's under Tools, References. If it's not set, you'll get a Compile Error: User-defined type is not defined.

To use with the reading pane, you need to disable conversation view.

See How to use Outlook's VBA Editor for instructions and screenshots.

Option Explicit
 Dim WithEvents objInspectors As Outlook.Inspectors
 Dim WithEvents objOpenInspector As Outlook.Inspector
 Dim WithEvents objMailItem As Outlook.MailItem
 Dim WithEvents myOlExp As Outlook.Explorer
 Dim sExplorer As Object
 Dim Document As Object
 Dim Msg

'Sets the zoom to the same value
' To use different values, replace msgzoom with the number
' in openinspector and selectchange macros
 Const MsgZoom = 200

Private Sub Application_Startup()
 Set objInspectors = Application.Inspectors
 Set myOlExp = Application.ActiveExplorer
 Set sExplorer = CreateObject("Redemption.SafeExplorer")
 End Sub

Private Sub Application_Quit()
 Set objOpenInspector = Nothing
 Set objInspectors = Nothing
 Set objMailItem = Nothing
 End Sub

Private Sub objInspectors_NewInspector(ByVal Inspector As Inspector)
 If Inspector.CurrentItem.Class = olMail Then
 Set objMailItem = Inspector.CurrentItem
 Set objOpenInspector = Inspector

End If
 End Sub
 Private Sub objOpenInspector_Close()
Set objMailItem = Nothing
 End Sub

Private Sub objOpenInspector_Activate()
Dim wdDoc As Word.Document
 Set wdDoc = objOpenInspector.WordEditor
 wdDoc.Windows(1).Panes(1).View.Zoom.Percentage = MsgZoom

End Sub

Private Sub myOlExp_SelectionChange()
On Error GoTo ErrHandler:
 Set Msg = Application.ActiveExplorer.Selection(1)
 Application.ActiveExplorer.RemoveFromSelection (Msg)
 Application.ActiveExplorer.AddToSelection (Msg)
 sExplorer.Item = Application.ActiveExplorer
 Set Document = sExplorer.ReadingPane.WordEditor
 Document.Windows.Item(1).View.Zoom.Percentage = MsgZoom
Exit Sub

ErrHandler:
    Exit Sub

End Sub

Zoom in Reading Pane or Open Message Video Tutorial

Not shown in the video: You need to set a reference to the Microsoft Word Object Library in the VBA's Editor. It's under Tools, References. If it's not set, you'll get a Compile Error: User-defined type is not defined..

Set the Zoom Level in Open Messages

You can use VBA to force the zoom level when you read incoming email in Outlook 2007 or newer, or when using Outlook 2003 with Word set as the email editor. Don't forget to set the desired zoom level in this line:
wdDoc.Windows(1).Panes(1).View.Zoom.Percentage = 150

This macro goes in ThisOutlookSession.

You need to set a reference to the Microsoft Word Object Library in the VBA's Editor. It's under Tools, References. If it's not set, you'll get a Compile Error: User-defined type is not defined.

Option Explicit
 Dim WithEvents objInspectors As Outlook.Inspectors
 Dim WithEvents objOpenInspector As Outlook.Inspector
 Dim WithEvents objMailItem As Outlook.MailItem
 

Private Sub Application_Startup()
 Set objInspectors = Application.Inspectors
 End Sub
 

Private Sub Application_Quit()
 Set objOpenInspector = Nothing
 Set objInspectors = Nothing
 Set objMailItem = Nothing
 End Sub
 

Private Sub objInspectors_NewInspector(ByVal Inspector As Inspector)
 If Inspector.CurrentItem.Class = olMail Then
 Set objMailItem = Inspector.CurrentItem
 Set objOpenInspector = Inspector
 
 End If
 End Sub

Private Sub objOpenInspector_Close()
 
Set objMailItem = Nothing
 End Sub
 

Private Sub objOpenInspector_Activate()
 
Dim wdDoc As Word.Document
 Set wdDoc = objOpenInspector.WordEditor
 wdDoc.Windows(1).Panes(1).View.Zoom.Percentage = 150
 
End Sub

Zoom Macro Video Tutorial

How to use the macro

First: You will need macro security set to low during testing.

To check your macro security in Outlook 2010 and up, go to File, Options, Trust Center and open Trust Center Settings, and change the Macro Settings. In Outlook 2007 and older, it’s at Tools, Macro Security. If Outlook tells you it needs to be restarted, close and reopen Outlook. Note: after you test the macro and see that it works, you can either leave macro security set to low or sign the macro.

Now open the VBA Editor by pressing Alt+F11 on your keyboard.

To use the macro code in ThisOutlookSession:

1. Set your macro security to Low in File, Options, Trust Center, Trust Center Settings, Macro Settings.
2. Open the VB editor using Alt+F11
3. Expand Project1 and double click on ThisOutlookSession.
   
4. Copy then paste the macro into ThisOutlookSession. (Click within the code, Select All using Ctrl+A, Ctrl+C to copy, Ctrl+V to paste.)
5. Set a reference to Microsoft Word in Tools, References
6. Click in the Application_Startup macro and press the Run button to kick start it without restarting Outlook.

Application_Startup macros run when Outlook starts. If you are using an Application_Startup macro you can test the macro without restarting Outlook by clicking in the first line of the Application_Startup macro then clicking the Run button on the toolbar or pressing F8.

More information as well as screenshots are at How to use the VBA Editor.