I know that you’re customer have been checking his spam folder and still the invoices are not available. One of my colleagues answered a similar post, you can refer to this link:

Hi businessherpagr!

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When invoices are sent directly from QuickBooks, they come from […]

Resolution for 'colleagues answered issue: 'I am initiating and sending invoices from QuickBooks Online to my customer’s email address, but my customer is not receiving them. He checked his spam folder as well' available: Yes.

The colleagues answered issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the colleagues answered issue yourself by looking for a resolution described in the article. If it is a complex colleagues answered issue or you are unable to solve the issue, you may contact us by clicking here or by using other colleagues answered support options.

For more information about resolving issues related to colleagues answered in Quickbooks/QBO or to get support for the issue 'I am initiating and sending invoices from QuickBooks Online to my customer’s email address, but my customer is not receiving them. He checked his spam folder as well', click the link below:

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