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Maestra tracks whether each customer’s email address is valid so you don’t send campaigns to addresses that no longer work. This keeps your sender reputation healthy and your deliverability high.

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Why email validity matters

Sending to addresses that don’t exist hurts your reputation with email providers. The more failed deliveries you generate, the more likely your future campaigns are to land in spam — even for customers with valid addresses. Maestra automatically flags addresses that look broken and stops sending to them. That protects your deliverability and avoids wasted load on sending infrastructure.
Email validity is shared across all Maestra projects. If an address is marked invalid based on failures on one project, it stays invalid everywhere.

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When an email is marked invalid

An email address becomes invalid in either of these cases:
  • A single delivery failure with the reason “Address does not exist” on any Maestra project.
  • Three consecutive delivery failures with the reasons “Address rejects mail” or “Unknown delivery error”, where at least 7 days pass between the first and last failure, and no one has manually marked the address as valid in between. These failures are also counted across all Maestra projects.

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When an email is temporarily invalid

If an address returns a “Mailbox full or inactive” failure, Maestra marks it temporarily invalid and blocks sending for a set period. Each repeat failure extends the block.
Failure numberBlock duration
1st failure7 days
2nd failure30 days
3rd failure90 days
4th failure180 days
5th and later360 days
After the block expires, Maestra can send to the address again. If the mailbox is still full or inactive, the next failure moves it to the next tier.

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How an email regains valid status

An invalid address can become valid again in any of these ways:
  • The customer opens a message, clicks a link, unsubscribes, or the system receives an auto-response within 36 hours of a send. Any of these signals on any Maestra project will revalidate the address.
  • An administrator manually marks the address as valid from the customer profile.
Manual revalidation is useful when you know an address is good — for example, the customer confirmed it through support — but Maestra hasn’t seen recent engagement to revalidate it automatically.

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How validity affects campaign sending

Validity controls which campaigns can reach an address:
  • Standard and opt-in sending profiles cannot send to invalid addresses. Maestra filters them out before the send.
  • Transactional sending profiles, or any campaign with the “Ignore contact validity” flag enabled, can still send to invalid addresses.
Sending to invalid addresses — even through a transactional profile or the ignore-validity flag — carries real reputation risk. Use it only for messages you’re certain must be delivered, like password resets or order confirmations, and only when you have reason to believe the address still works.
Keep in mind that ignoring validity does not exempt you from anti-spam law. CAN-SPAM, CCPA, and similar regulations still apply to every send, including transactional ones.