Have a look at the list of problems responsible for causing QuickBooks Won't Email invoices: if the domain admin was blocked, email preferences were set incorrectly, if you have not set the email provider's account security settings, if QuickBooks was installed incorrectly, if the MAPI32.dll file is damaged, if the outlook was installed in a wrong way, outlook runs in the background while you send invoices. If you want to fix the issue with the most effective methods then follow this linked guide. Dial this number 1.800.579.0391 if you need support from our QB experts.