Articles on: Deliverability And Warming

Understand Sender Health

Understand Sender Health


Purpose


Sender health tells you how well a specific mailbox is performing as a sending identity. Low health means deliverability risk — your emails are more likely to land in spam. This article explains what the health score means, what causes it to drop, and how to respond.


What Is the Health Score?


The health score is a composite signal from SuperSend's warming network. It reflects how often warming emails sent from your mailbox are landing in inboxes vs. spam, how often they're being opened, and whether recipients are marking them as spam.


Score thresholds:

  • ≥80% (green) — Healthy. Good to use in active campaigns.
  • 60–79% (yellow) — Caution. Reduce campaign volume while investigating.
  • <60% (red) — Problem. Pause campaign sending from this mailbox until resolved.


You can see each mailbox's health score in the Warming dashboard → Warming Senders table → Health column.


What Affects Health Score


Inbox rate — The most direct factor. If warming emails from your mailbox land in spam instead of inbox, health drops. This is what the Inbox Rate column measures.


Engagement — Whether warming emails get opened and replied to. Low engagement suggests the mailbox isn't building trust with receiving mail servers.


Spam complaints — If recipients mark warming emails as spam, health drops significantly and quickly.


Provider-level limits — Some providers (especially newer accounts) have sending limits that, if hit repeatedly, can trigger deliverability suppression.


Authentication issues — If SPF, DKIM, or DMARC records aren't properly configured on the sending domain, emails are more likely to be filtered as spam regardless of warming.


How to Read the Signals Together


The warming dashboard gives you three signals to interpret together:


Health Score + Inbox Rate together:

  • High health + high inbox rate (>95%): your mailbox is in great shape.
  • High health + declining inbox rate: early warning sign. Watch it — don't scale yet.
  • Low health + low inbox rate (<85%): actively problematic. Pause campaign sends from this mailbox.


Inbox Rate by Provider:

The "Inbox Placement by Provider" row at the top of the warming dashboard breaks down inbox rates by receiving provider (Google, Outlook, Yahoo, etc.). This is important because a single number like "92% inbox rate" can hide a serious problem. 92% overall might mean 98% inbox on Google but only 65% on Outlook. If your campaign targets a lot of Outlook-hosted companies, that 65% rate is what matters.


Volume (Sent Today / Max Per Day):

If a mailbox is consistently hitting its daily max, that's fine. If it's sending far less than max, check if there's a connection issue or if warming has been paused.


Senders with a ⚠ Problem Flag


If a mailbox shows a red ⚠ warning icon in the Email column of the warming table, it's been flagged as a problem. Common reasons:


  • Mailbox authentication failed (password changed, OAuth token revoked)
  • Provider has suspended or throttled the account
  • Inbox rate has been critically low for multiple days in a row


To investigate: Click the gear icon on that mailbox row to open Edit Sender Details. Check the connection status and SMTP/IMAP settings. Re-authenticate if needed.


Click Need Attention at the top of the warming dashboard to filter to just these problem senders.


Adjusting Warming Settings


From the gear icon on any sender row (Warming dashboard → sender table), you can edit:


  • Warming on/off — toggle whether this mailbox participates in warming
  • Max per day — the daily sending limit for warming emails
  • Warming ramp — how aggressively volume increases during initial warmup
  • Campaign ramp — how campaign sends are ramped for this mailbox


Be conservative with campaign ramp settings for new mailboxes. Scaling campaign sends before the health score stabilizes is the most common cause of deliverability problems.


What to Do When Health Drops


  1. Reduce campaign volume from the affected mailbox immediately. Go to the sender profile → edit the mailbox's daily limit, or temporarily remove the mailbox from the profile.


  1. Check domain authentication. Verify that SPF, DKIM, and DMARC records are correctly configured on the sending domain. A single misconfiguration can cause systemic inbox rate problems across every mailbox on that domain.


  1. Run a placement test. Placement tests give you a provider-by-provider breakdown of where your emails land. See Placement Tests Overview.


  1. Let warming run. If you've reduced volume and fixed any authentication issues, give the mailbox 5–7 days of clean warming sends before checking the health score again. Health scores do recover, but not instantly.


  1. Don't ignore yellow. A yellow health score that you ignore can become red within a week if campaign volume continues to increase.


Expected Result


You can interpret a mailbox's health score and inbox rate, identify problem senders before they damage campaign performance, and know what actions to take when signals turn yellow or red.


Troubleshooting


  • Issue: Health appears good but open rates on campaigns are dropping.

Fix: Good warming health doesn't guarantee good campaign deliverability — it means the mailbox infrastructure is healthy. Low open rates can also be caused by poor subject lines, unengaged audiences, or targeting contacts at providers where your mailbox performs poorly. Run a placement test.


  • Issue: Health score is high on the warming dashboard but a specific campaign has terrible inbox placement.

Fix: Campaign content (links, certain phrases, image-heavy HTML) can trigger spam filters even when the mailbox itself is healthy. Try a plain-text version and test without any links.



Updated on: 17/03/2026

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