Woocommerce not sending emails

Hi @doug54arpley,

Thanks for reaching out, and I am so sorry to hear about the trouble.

I think there are actually two separate things going on here, and the log entry you found isn’t the cause of the missing order confirmations.

“instock_notifier_users_mailout” isn’t a WooCommerce core order email — that naming pattern comes from a third-party “Back in Stock” / waitlist notifier plugin (something like Instock Notifier for WooCommerce, Back In Stock Notifier, or a similar waitlist add-on). Those plugins let site visitors, including guests who aren’t logged in, sign up to be emailed when an out-of-stock product comes back. The “recipient”: “guest” in that log line looks like a label meaning “this subscriber wasn’t a logged-in customer,” not an actual email address — so somewhere in that plugin’s subscriber data, a guest signup doesn’t have a valid email stored against it. When the plugin tries to send the back-in-stock notice, it hands WP Mail SMTP an empty “to” field, and WP Mail SMTP correctly refuses to send it. That’s expected behavior, not a bug in WP Mail SMTP, and it’s unrelated to your order emails.

For the actual missing order confirmation, a few things worth checking:

1. In WooCommerce → Status → Logs, look for an entry tied to the actual order number from that day (not the instock_notifier one) — that should show whether the order email itself failed and why.
2. In WooCommerce → Settings → Emails, confirm “New order”/”Processing order”/”Completed order” are enabled and there’s no unexpected recipient override.
3. If you have WP Mail SMTP’s Email Log enabled (Settings → Email Log), check whether an email was even attempted for that specific guest order, and what address it was sent to.
4. Since it worked on your own test purchase but failed for a real guest customer, that points toward something on the checkout side rather than SMTP delivery — worth checking whether a caching plugin, checkout field editor, or consent/GDPR plugin might be stripping or blocking the email field specifically during guest checkout.

I hope this helps. Thanks 🙂

Hi @doug54arpley ,

Thanks for the update. If new-customer emails are failing too, this points to something at the mail-sending level, not WooCommerce specifically.

Mail reaching only her alternate address while others fail often means the SMTP provider is still in sandbox/test mode, only delivering to pre-verified recipients (common with SES, Mailgun, or SendGrid on a limited plan).

Could you check which mailer is set up in WP Mail SMTP → Settings, and whether it’s in sandbox/test mode? Also, let me know if she is seeing the same error like you mentioned before.

Thanks, and please let me know.