Email Center statistics: delivery, bounce and complaint rates, and what they tell you

E-mail·· 40 views· 3 min read

The short answer: statistics show your sends by status and by day, with three rates: delivery, bounce and complaint. You see them under Statistics on the Transactional e-mail page in My MozOut, or with GET /v1/email/stats. By default they cover the last 30 days; the period can be up to 366 days.

What each number means

Field What it says
messages How many e-mails you asked to send
recipients How many recipients, counting to, cc and bcc
credits_spent Credits used in the period
by_status How many ended in each status: delivered, bounced, complained, sent, failed
delivery_rate The percentage of recipients whose e-mail was delivered
bounce_rate The percentage of recipients that bounced
complaint_rate The percentage of recipients that marked it as spam
by_day The same numbers, day by day

Rates are worked out over recipients, not e-mails: an e-mail with three recipients counts three times.

Choosing the period

GET https://api.mozout.com/v1/email/stats?from=2026-10-01&to=2026-10-31

Dates go as YYYY-MM-DD. A period longer than 366 days gives a validation error.

How to read the rates

Sign What it usually is What to do
Bounces going up Old or mistyped addresses in your system Validate addresses at sign-up and review the suppression list
Complaints above zero Someone got an e-mail they did not expect, or the message looks like advertising Take promotions out of service e-mails and review the sender
Delivery dropping with no bounces Many still at sent, waiting for the receiving side Wait and look again; if nothing changes, open a support ticket
Failed Balance, an unverified domain or delivery impossible See each error in the log
Complaints are the most serious number. With a transactional e-mail, the customer asked for that message. If they mark it as spam, something is wrong: the sender is not recognised, the subject misleads, or there is advertising mixed in.
Check the statistics after every change: a new template, a new domain, a new sender. A bad change shows first in bounces and complaints.

Your rates changed and you do not know why? Open a support ticket with the period.

Open a support ticket

SEE ALSO

Transactional e-mail statuses: sent, delivered, bounced, complained and failed explained

The Email Center log: finding an e-mail, filtering it and why the content goes after 30 days

The Email Center suppression list: why an address stops receiving and how to remove it

A new domain sending e-mail: how to build a reputation without landing in spam

SPF, DKIM and DMARC: why your e-mail lands in spam

Password reset, order and invoice e-mails: what a good transactional message says, with examples

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