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When the system email cannot be sent out, should we first look at the bounce rate or the complaint rate

📅 2026-11-01 👁️ 0

When the system email cannot be sent, should you first look at the bounce rate or the complaint rate? Look at the bounce rate first. A bounce indicates that the delivery step was rejected, directly corresponding to the address quality and server reputation; the complaint rate occurs after the email is received, reflecting the degree to which the content is judged as spam, and it has a value only when the email is still being delivered normally. Therefore, the troubleshooting sequence is to first look at the total bounce rate and hard bounce rate to confirm that the delivery channel is still alive, and then look at the complaint rate and unsubscribe rate to judge the issues with the list and content.

The meanings of the two indicators are different

The bounce rate is the percentage of outgoing emails that are returned, and hard bounces refer to permanent rejections such as non-existent addresses or domain expiration. Pushwoosh provided the criteria for the 2026 email marketing indicators as the total bounce rate “Total bounce rate should stay below 2%” and hard bounces “Hard bounces should be under 0.5%”.Mailmend's bounce rate statistics page wrote that globally, 'Hard bounce rates average 0.19% globally.' Additionally, 'At least 25% of email databases decay annually.' This means that at least one quarter of the address databases will age over time.

The complaint rate is the proportion of recipients who click on 'Report spam mail', the threshold is much stricter than bounce rate. Pushwoosh's standard is 'Keep spam complaints below 0.1%,' and anything above 0.3% is considered severe ("Anything above 0.3% is critical"). These two indicators, when mixed together, can lead to incorrect conclusions: the hard bounce rate is less than half a percentage point lower, but half of the addresses in the list are very old, and delivery will still end up in the spam folder.

Investigation sequence

  1. First, confirm the channel itself: send a test email directly from the server to the commonly used email address to see if it can enter the inbox. This step excludes issues such as port, DNS records, and service provider blocking.
  2. Then, check the bounce details: distinguish between soft bounces (temporary rejection by the recipient, quota full) and hard bounces. The proportion of hard bounces close to 0.19% of the global average is normal; if it is much higher than this, it indicates that there are invalid addresses in the list.
  3. Then look at the complaint rate and unsubscribe rate: Pushwoosh gives the unsubscribe watermark as “Keep your unsubscribe rate below 0.2%”, anything above 0.5% is a clear signal. If the complaint rate is not high but the unsubscribe rate spikes, it is usually a mismatch between the content and the subscription expectations.
  4. Finally, adjust the sending strategy: reduce frequency, break bulk sends into event triggers, and conduct a second confirmation for the list.
Indicator The口径 verified on the day What to look at first when exceeding the threshold
Total bounce rate Should be less than 2% Domain and sending IP reputation
Hard bounce rate Should be less than 0.5%, global average 0.19% Invalid addresses in the list
Complaint rate Should be less than 0.1%, serious if higher than 0.3% Is the content consistent with the subscription expectations
Unsubscribe rate Should be less than 0.2%, above 0.5% is a signal Frequency of transmission and population segmentation
Address aging At least 25% per year Time of last subscription confirmation

Where does the address quality come from

The source of address aging is very specific: email suspension after staff leave, one-time filled test addresses, lists imported during the activity period without secondary confirmation. The email subscription feature in AnQiCMS was added to the background with the message list in v3.6.5, subscribers can directly enter the list from the site side, and administrators can handle the list in the background; email reminders bear the notification triggered by events,配合full-site replacement tools maintained contact information and links, both separately maintained so as not to mix system notifications and marketing mass sending into one path.

Maintain three suggestions on actions: Regularly group long-term inactive addresses separately, reduce frequency first and then decide whether to clean up; enable captcha on the form side to reduce the bulk writing of spam addresses by robots; when importing historical lists, send them in small batches first, then release them in large quantities after checking the bounce details.

Reminders and subscriptions are divided into two layers

System emails cannot be sent, and it is often not that 'a marketing email is rejected', but that reminders triggered by background events are treated as spam. The difference lies in:

  • The recipient of the reminder triggered by the event clearly expects this letter, the complaint rate is low, and the bounce mainly reflects whether the address is still valid.
  • The push of the subscription list is sent in batches, the complaint rate and unsubscribe rate are the main risks, and the recipient can report at any time.

Mixing two types of emails in the same sending channel and the same signature will affect the delivery of reminders. The feasible approach is to divide channels and themes, and always keep a visible unsubscribe link in the subscription email.

Common questions

Does a low bounce rate mean that the list is healthy?No explanation. The hard bounce rate is low, but the addresses are aging seriously, the delivery success rate will decrease, and the complaint rate and unsubscribe rate are the signals of the later stage of aging.

Should you clean up the addresses first or change the service provider first?Check the detailed bounce back information. If the same batch of addresses frequently bounce back soft, the problem is with the temporary rejection on the other side; if there is a concentration of hard bounce back, it is more cost-effective to clean up the list first.

What level of complaint rate is considered safe?The criteria for the day's verification is that less than 0.1% is healthy, more than 0.3% is severe, and when reaching a severe level, the immediate stop and re-examination of the population and content should be carried out.

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