Understanding Email Bounces: Hard Bounces, Soft Bounces, and Hotmail/AOL Issues

If you've noticed contacts — especially those with Hotmail, Outlook, AOL, Yahoo, or Earthlink addresses — showing up as bounced or unsubscribed in MonkeyPod, you're not alone. This article explains what email bounces are, how to find and interpret them in MonkeyPod, and what you can (and can't) do about them.

What is an email bounce?

A bounce occurs when an email you send cannot be delivered to a recipient's inbox and their mail server sends back an error. MonkeyPod records these errors and automatically suppresses future sends to bounced addresses to protect your sender reputation.

There are two types of bounces:

Hard bounces are permanent delivery failures. Common causes include:

• The email address doesn't exist or has been deleted
• The domain is invalid or no longer active
• The recipient's mail server has permanently blocked your sending address

MonkeyPod will not retry hard-bounced addresses. Because continuing to send to invalid addresses damages your sender reputation, these contacts are suppressed from future campaigns.

Soft bounces are temporary delivery failures. Common causes include:

• The recipient's mailbox is full
• The recipient's mail server was temporarily unavailable
• The message was too large to deliver

MonkeyPod may retry soft-bounced addresses in future campaigns, depending on the nature of the error. If a contact soft-bounces repeatedly, MonkeyPod may eventually treat it as a hard bounce.

How to find bounced contacts in MonkeyPod

There are a few places in MonkeyPod where you can see bounce information:

Bounce rate over time (by list)

In the main menu, go to Email Outreach → Bounces. This shows a time-series chart of bounce rates for each of your email lists, which is useful for spotting trends or a sudden spike after a campaign sends.

Individual bounced contacts (by list)

To see which specific contacts have bounced, go to Email Outreach → Email Lists, then select any list. On the Subscribers List tab, use the Unsubscribed filter. Contacts who have bounced will appear here alongside manually unsubscribed contacts — the status note on each contact will indicate whether they were unsubscribed manually or as a result of a bounce.

Bounce stats for a specific campaign

If you want to see how many bounces a particular campaign generated, go to Email Outreach → View & Create Campaigns, click into a sent campaign, and look at the Summary tab. It shows a total Bounces count and Bounce Rate for that send.

Why do Hotmail, AOL, and Yahoo addresses bounce so often?

Major consumer email providers — particularly Microsoft (Hotmail/Outlook), AOL, Yahoo, and Earthlink — use significantly more aggressive spam filtering than other providers. This is by design: these services host hundreds of millions of personal inboxes and prioritize filtering out anything that looks like bulk email.

Here's what makes them different:

• Microsoft uses a reputation-scoring system that evaluates senders based on complaint rates, bounce history, and sending patterns. If your domain or sending IP scores poorly — even temporarily — Microsoft may issue a bulk bounce, rejecting a large group of addresses at once rather than evaluating them individually.
• AOL and Yahoo operate a similar feedback loop system. A certain percentage of recipients flagging your emails as spam can trigger broad filtering rules that affect other recipients on those platforms.
• Earthlink is a legacy provider with older, stricter filtering infrastructure that doesn't handle bulk nonprofit email well.

None of this is specific to MonkeyPod. It's a known challenge across the email industry, and it affects organizations of all sizes.

The daily re-bounce loop: what's happening and why

Some users notice that when they manually re-subscribe a contact who bounced, that same contact bounces again the very next day. This cycle can repeat indefinitely, and it's one of the most frustrating email deliverability issues nonprofits encounter.

Here's why it happens:

When MonkeyPod removes a contact from the suppression list, that clears the record on MonkeyPod's side. But if the underlying reason the contact bounced — usually a sender reputation problem with Microsoft's filtering system — hasn't been resolved, the next email sent to that address will be rejected again, and the contact will bounce right back onto the suppression list.

In short: re-subscribing a contact doesn't fix the root cause. It just resets the symptom.

This loop is especially common with Hotmail and Outlook addresses because Microsoft's filtering evaluates your sending domain's overall reputation, not just individual emails. If enough of your emails to Microsoft-hosted addresses are being flagged or rejected, all future sends to those addresses will continue to fail until your reputation improves.

What you can do: See the DNS and authentication section below for steps that directly improve your standing with Microsoft's filters. And ask affected donors to add your sending address to their contacts or safe senders list. This is the single most effective workaround at the individual recipient level (more on this below).

What you shouldn't do: Repeatedly re-subscribing bounced Hotmail/Outlook contacts without addressing the root cause will not resolve the loop and may actually reinforce your poor reputation score by generating additional bounce signals.

What you can do to improve deliverability

Some deliverability factors are within your control; others are not.

Things that help (and are in your control)

1. Ensure your DNS authentication records are properly configured

The single most important technical factor in your deliverability with Microsoft and other major providers is whether your domain has valid SPF, DKIM, and DMARC records. These records tell receiving mail servers that MonkeyPod is authorized to send email on your behalf.

If these records are missing or misconfigured, Microsoft and others are much more likely to filter your emails as spam — or bulk-bounce them entirely. See Learn About Email Deliverability (DNS Settings) for setup instructions.

2. Keep your list clean

Remove contacts who haven't engaged with your emails in a long time. Sending repeatedly to inactive or invalid addresses drives up your bounce rate and spam complaint rate, both of which damage your sender reputation over time.

3. Ask donors to whitelist your sending address

This is the most reliable fix at the individual recipient level. Donors can add your sending address to their contacts or safe senders list in Outlook/Hotmail, which tells Microsoft to bypass spam filtering for your emails entirely.

You can include a note in your email footer or a follow-up message asking donors to do this:

For Outlook/Hotmail users specifically, the steps are: Settings → Junk email → Safe senders → Add your sending address.

Things that are largely outside your control

Microsoft's internal filtering decisions are opaque. Microsoft does not publish the exact thresholds it uses, and even senders with perfect authentication and clean lists can be caught in bulk bounces. Reputation recovery takes time and consistent, clean sending behavior — there's no instant fix.

Consumer provider feedback loops mean that a small number of recipients clicking "mark as spam" can trigger broader filtering for your entire domain on that platform. You can't control individual recipients' behavior.

The best long-term approach is consistent: maintain clean lists, keep authentication records up to date, and encourage engagement so your emails are opened, not filtered.

When is it appropriate to re-subscribe a bounced contact?

Use your judgment based on the bounce type and context:

When in doubt, err on the side of caution. Re-subscribing contacts who continue to bounce can harm your sender reputation.

Have questions not covered here? Contact MonkeyPod support.