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We've been alerted about this behavior in the system, mgordon523.
Something triggered the settings and our Product Engineers are looking into this now to determine why attachments are not being sent with emails.
For now, you can turn the settings back on. Then, manually download the estimate and send it to your client outside QuickBooks.
Let me show you how:
I've added this link to learn how an estimate works in QuickBooks: Set up and use estimates.
Let me know if you need anything else aside from creating estimates. I'll be around to help you.