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Level 4
February 19, 2026
Question

Recommended Approach to Reintroduce Bounced Emails into Marketing Campaigns

  • February 19, 2026
  • 1 reply
  • 36 views

Hi Team,

We currently have a process where an email is marked ineligible from Marketo after 5 soft bounces or a Category 2 hard bounce. However, we’re planning to use ZeroBounce to re-validate those email addresses after a defined period (for example, after several months of being ineligible).

ZeroBounce provides results such as valid, invalid, and catch-all. Our intention is to carefully reintroduce only the valid email addresses through a separate warm-up campaign, rather than adding them directly back into regular marketing sends. The idea is to first monitor engagement and mailbox health before including them in standard campaigns. For example, emails that previously soft bounced due to mailbox full may become deliverable again over time.

We would like guidance on the following:

  • What are the best practices for safely re-engaging previously bounced emails without negatively impacting our IP and domain reputation? Since we use the same sending domain for a specific brand so bringing back those emails and sending emails will that impact our IP ?

  • Is using a separate warm-up campaign the recommended approach before resuming regular sends?

  • If these emails bounce again after reactivation, what is the recommended best practice? Should they be permanently ineligible, or is there a recommended retry limit?

  • Are there any additional compliance or deliverability safeguards we should follow during this process?

Our goal is to follow a structured and compliant approach while protecting our sender reputation.

Any guidance or recommendations would be greatly appreciated.

Regards,
Akshat

1 reply

Darshil_Shah1
Community Advisor and Adobe Champion
Community Advisor and Adobe Champion
February 20, 2026

What are the best practices for safely re-engaging previously bounced emails without negatively impacting our IP and domain reputation? Since we use the same sending domain for a specific brand so bringing back those emails and sending emails will that impact our IP ?

Re-introducing previously bounced emails needs to be handled very carefully — especially if you’re using the same sending domain/IP for your main brand.

A few best practices:

Even if ZeroBounce marks an address as valid, I would:

  • Exclude prior hard bounces permanently (especially Category 1/2)

  • Be cautious with repeated soft bounces (5+ historically is already a strong signal)

  • Treat catch-alls as high risk unless strategically important

Remember that validation tools reduce risk, but they don’t override ISP history. Example: If Gmail previously rejected it repeatedly, that reputation memory may still exist.

Is using a separate warm-up campaign the recommended approach before resuming regular sends?

 

A separate, low-volume warm-up campaign is absolutely the right approach.

Best practice would be:

  • Very small batch size

  • Highly engaging content that has performed well in the past (not generic promotional email)

  • Closely monitor bounce rate, spam complaints, and engagement

  • Gradually scale only if metrics are healthy

I would not drop them directly to your regular sends.

If these emails bounce again after reactivation, what is the recommended best practice? Should they be permanently ineligible, or is there a recommended retry limit?

 

If an address re-bounces after validation then update them to permanently ineligible and do not retry repeatedly as that might impact your reputation. Repeated retries are more damaging than the original bounce.

Are there any additional compliance or deliverability safeguards we should follow during this process?

If you’re sending from the same branded domain and IP pool, yes poor reintroduction strategy can impact overall reputation. I would advise keeping the volume low, monitoring domain-level metrics, not just at the campaign level (you might need a deliverability monitoring tool for this).

Aside from this, you can also add additional safegurads, such as adding engagement criteria (e.g., no opens/form/registered/attended event fills in 12 months = don’t reintroduce, make sure you're compliant in sending emails (GDPR/consent validity if applicable), and lastly, closely monitor your domain and IP reputation and blocklists.

 

I hope you find this helpful. Pls let us know if you have any follow-up questions.

ashah123Author
Level 4
February 20, 2026

@Darshil_Shah1 

First of all, thank you for explaining everything in such detail and with examples — I really appreciate the help. I have a few follow-up questions:

  1. Bounce categories clarification
    As you mentioned earlier, Hard Bounce Category 1 and 2 should be considered permanent failures. However, in some documentation, we saw that Category 1 was treated as a temporary bounce, and when we have retried sending, the email was delivered successfully. Could you please clarify whether Category 1 should always be treated as permanent, or if there are exceptions?

  2. Deliverability monitoring tool (Bird)
    We are using the deliverability monitoring tool (Bird) integrated with Adobe Marketo Engage for inbox placement and monitoring. Could you please confirm if this tool is sufficient, or if you recommend monitoring anything additional outside of Bird?

  3. Domain-level metrics
    You mentioned monitoring domain-level metrics. Could you please elaborate on:

    • What specific metrics we should focus on?

    • Where exactly we can monitor these?

    • Any thresholds or benchmarks we should maintain?

  4. Shared IP and sending domain
    Since we are on Marketo’s shared IP, I understand we are using Marketo-managed IP addresses, which may vary between sends. However, our sending domain remains consistent for our brand. Could you please confirm if this setup is correct and suggestions here?

  5. ZeroBounce and retry logic
    Regarding list validation using ZeroBounce — just to confirm my understanding:
    If an email address passes validation but still bounces again after sending, it should then be treated as a permanent failure and suppressed right ? The below logic you added was to consider before the records pass through zeroubounce correct ?

Aside from this, you can also add additional safegurads, such as adding engagement criteria (e.g., no opens/form/registered/attended event fills in 12 months = don’t reintroduce)

I will definitely consider and implement the suggestions you shared. Your feedback on the above points will help us ensure we’re following the right approach.

Thanks again for your support.

Darshil_Shah1
Community Advisor and Adobe Champion
Community Advisor and Adobe Champion
February 20, 2026
  1. Bounce categories clarification:

You're right to question this. To summarize:

  • Category 2 hard bouncesTreat as permanent failures (invalid domain, user unknown, etc.). Do not retry.

  • Category 1 bounces: These can sometimes be transient (e.g., temporary technical rejection), even though they’re labeled “hard.”

So Category 1 is not always permanent. However, in case the same address hits multiple Category 1 bounces, or it previously had repeated soft bounces before that, I'd consider it a high risk and suppress.

  1. Deliverability monitoring tool (Bird):

Inbox monitoring tools are good for inbox placement testing, blacklist monitoring, and overall domain reputation (domain reputation is more under your control than IP monitoring, since you're on a shared IP), but they don’t replace monitoring your actual campaign metrics. You should still look for hard bounce, soft bounce, spam complaints, engagement over time, etc. It's important you keep a watch on both (Bird and campaign performance). 

  1. Domain-level metrics:

Yes, you're right: since you’re on a shared IP, your domain's reputation matters more than your IP's (and the latter is under your control more than the former). If you’re not using Gmail Postmaster Tools yet, I would recommend it for domain-level visibility. It helps with spam rate + domain reputation.

  1. Shared IP and sending domain:

That's correct. Dedicated IP, on the other hand, gives you more control over your reputation, but you'd need at least ~100,000 emails to keep it warm enough. If your email volume is lower than that, you're better off on the Shared IP.

  1. ZeroBounce and retry logic

Correct, the engagement safeguard I suggested applies before reintroducing them. So the flow would be:

  • Previously bounced

  • Validate via ZeroBounce

  • Only “valid” pass forward

  • Apply engagement filter (e.g., active within last 12 months)

  • Send emails through the reactivation campaign

If they bounce again after reactivation, then you permanently suppress them.

I hope you find this helpful.