What is the QBMAPI64 “Out of Memory” Error?

The QBMAPI64.exe / QBMAPI64.dll “Out of Memory” error typically appears in QuickBooks Desktop when the program tries to send emails (usually via Outlook) or interact with Windows MAPI services and fails due to resource, integration, or configuration issues.

It can show up as:

• “QBMAPI64 out of memory”
• “QuickBooks has stopped working”
• Crashes when sending invoices or forms by email

The error is tied to QuickBooks’ Messaging Application Programming Interface (MAPI) component used for email integration.

Common Causes

1. Microsoft Outlook or Office corruption

• Broken Outlook profile
• Faulty Office installation or updates

1. QuickBooks installation issues

• Damaged program files
• Missing or corrupted components

1. Windows memory or system resource conflicts

• Low available virtual memory
• System limits or unstable background processes

1. Email integration conflicts

• Switching between Web Mail and Outlook
• MAPI configuration mismatch

1. Recent Windows or QuickBooks updates

• Known compatibility issues after updates (frequently reported)

Symptoms

• QuickBooks crashes when clicking Send Forms
• Error appears when emailing invoices/estimates
• Outlook opens with attachment errors or freezes
• QuickBooks shuts down unexpectedly after popup

Fixes & Workarounds (Most Effective First)

1. Restart and run QuickBooks as Administrator

• Right-click QuickBooks → Run as Administrator
• Also ensure Outlook is closed before testing

2. Repair QuickBooks installation

• Go to Windows Apps & Features
• Select QuickBooks → Repair
• Restart system afterward

3. Reinstall or repair Microsoft Office / Outlook

This is one of the most commonly reported fixes:

• Uninstall Office completely
• Reinstall latest version
• Rebuild Outlook profile

4. Increase Virtual Memory (Paging File)

• Windows Settings → System → Performance → Advanced
• Increase paging file (e.g., 4GB–12GB minimum depending on RAM)

5. Clear Office Document Cache (if Excel/Office is involved)

Some users resolved it by:

• Excel → Options → Save
• Clear cached Office files
• Reduce cache retention time

6. Update QuickBooks and Windows

• Install latest QuickBooks release
• Run Windows Update fully

7. Run QuickBooks Tool Hub

Use:

• Program Problems tool
• Quick Fix my Program
• Install Diagnostic Tool

8. Switch email method in QuickBooks

• Edit → Preferences → Send Forms
• Try switching:
• Outlook → Web Mail (or vice versa)

9. Reinstall QuickBooks (last resort)

If corruption persists:

• Backup company file
• Clean uninstall QuickBooks
• Reinstall latest version

When to Suspect a Deeper Issue

If the error:

• Started immediately after a Windows/QuickBooks update
• Happens on multiple computers
• Persists after reinstall

Then it is likely a known compatibility bug between QuickBooks MAPI (qbmapi64) and Outlook/Windows updates, not a local PC issue.

Key Takeaway

The QBMAPI64 “out of memory” error is rarely a true RAM issue. It is usually caused by:

• Outlook/MAPI integration problems
• Corrupt Office installation
• QuickBooks update compatibility bugs