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Last updated on Aug 20, 2026
Maxio blocks you from turning on e-Bill delivery for a Customer that has no email address, and rejects an obviously malformed one the moment you type it into the Email field. Typing an invalid address directly into a Customer's Email field in Maxio triggers this validation immediately, before you can save the record.

QuickBooks Desktop applies no equivalent check to its own Customer records: it accepts an address like notvalid.com without complaint. Maxio pulls a Customer's email address back from QuickBooks Desktop on every sync, so a bad or missing address that exists there lands in the Customer's QuickBooks Billing Profile in Maxio too, without ever passing through the validation shown above. A Customer whose Email field reached this state through a sync shows no warning in Maxio, whether the address that came over is invalid or missing entirely, as the two panels below show.


The rejection only surfaces later, when Maxio syncs an Invoice or Credit Memo for that Customer with the Invoice Email Preference turned on, and QuickBooks Desktop rejects the address it currently holds.
QuickBooks Desktop returns an error similar to There was an error when saving an Invoice/Credit Memo. QuickBooks error message: The email address specified for this customer is invalid, and the transaction is marked 'To be e-mailed.' when one of the Invoices or Credit Memos in the sync queue belongs to a Customer whose primary email address is currently invalid or missing in QuickBooks Desktop.
Fix the address in whichever system should own it going forward, then sync again so the corrected value reaches both sides.
To fix a bad or missing primary email address
If you do not want the transaction emailed at all, turn off the Invoice Email Preference on the Customer or Job instead of chasing down the email address. If a large number of Customers are affected, for example after an import, contact support@maxio.com for help correcting them in bulk.
Sending a Credit Memo can also fail with There was an error when saving a Credit Memo. QuickBooks error message: The Cc email address specified for this customer is invalid, and the transaction is marked 'To be e-mailed.'
Maxio's QuickBooks Desktop integration has no field of its own for a Customer's Cc email address. The sync only ever sends a Customer's primary email address to QuickBooks Desktop; it never reads or writes a Cc value. This means the invalid Cc address was set directly in QuickBooks Desktop, independent of anything Maxio manages, so editing the Customer's address on its QuickBooks Billing Profile tab in Maxio has no effect on this error.
To fix an invalid Cc email address
Since QuickBooks Desktop accepts a primary email address in any format, the best way to catch a bad one before it blocks an Invoice or Credit Memo sync is to manage it from the Maxio side and let Maxio's own validation do the work.
For how the To Be Emailed queue and the Invoice Email Preference setting interact between Maxio and QuickBooks Desktop, see Sync QuickBooks Invoices.
For how a Customer's fields, including its email address, sync between Maxio and QuickBooks Desktop, see Sync QuickBooks Customers.
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