Glossary
Email deliverability glossary
Plain definitions for people who send email through Amazon SES. Each entry says what the term means, where it shows up in SES, and what to watch so it never becomes the reason AWS pauses your account.
36 terms
5 topics
Written for SES senders, checked against how SendScope works
Start here
Four terms worth knowing first
If you only read a few entries, read these. They cover the numbers AWS reviews, the list that protects them and the record that keeps your mail trusted.
Bounces and complaints
Bounce rate
Email bounce rate is the share of your mail that bounced permanently. Amazon SES puts an account under review when its bounce rate reaches 5%, and can pause sending at 10%.
Read the definitionBounces and complaints
Complaint rate
Complaint rate is the share of your mail that recipients marked as spam and that was reported back to SES. Amazon SES puts an account under review at a 0.1% complaint rate, roughly one complaint per 1,000 messages.
Read the definitionAuthentication
DMARC
DMARC (Domain-based Message Authentication, Reporting and Conformance) is a DNS record that tells receiving servers what to do with mail that fails SPF and DKIM checks for your domain, and where to send reports about it.
Read the definitionBounces and complaints
Suppression list
An email suppression list is a list of addresses your sending platform will not send to, usually because they hard bounced or complained. It protects your bounce and complaint rates by stopping repeat sends.
Read the definitionNo term matches that search. Try a shorter word, or clear the filter.
Bounces and complaints
The two rates AWS reviews your account on, and the list that keeps them down.
Bounce rate
Email bounce rate is the share of your mail that bounced permanently. Amazon SES puts an account under review when its bounce rate reaches 5%, and can pause sending at 10%.
Read the definitionComplaint rate
Complaint rate is the share of your mail that recipients marked as spam and that was reported back to SES. Amazon SES puts an account under review at a 0.1% complaint rate, roughly one complaint per 1,000 messages.
Read the definitionHard bounce
A hard bounce is a permanent delivery failure. The receiving server has said the message can never be delivered to that address, usually because the address does not exist or the domain is invalid.
Read the definitionHard bounce vs soft bounce
A hard bounce is permanent and will never succeed, such as an address that does not exist. A soft bounce is temporary and may succeed later, such as a full mailbox. Only hard bounces count toward your Amazon SES bounce rate.
Read the definitionSMTP error codes
SMTP error codes are the numeric replies a receiving mail server gives when it refuses a message. A code starting with 4 is a temporary failure and one starting with 5 is permanent.
Read the definitionSoft bounce
A soft bounce is a temporary delivery failure. The address is valid, but the message could not be delivered right now, for example because the mailbox is full or the receiving server is busy.
Read the definitionSpam trap
A spam trap is an email address that looks real but is used to catch senders with poor list practices. Mail to a trap does not bounce in a useful way, and sending to one can get you blocklisted.
Read the definitionSuppression list
An email suppression list is a list of addresses your sending platform will not send to, usually because they hard bounced or complained. It protects your bounce and complaint rates by stopping repeat sends.
Read the definitionAuthentication
SPF, DKIM, DMARC and the DNS records that prove your mail is yours.
BIMI
BIMI (Brand Indicators for Message Identification) is a DNS record that lets supporting mailbox providers show your brand logo next to your emails. It requires an enforced DMARC policy.
Read the definitionDKIM
DKIM (DomainKeys Identified Mail) adds a digital signature to each email. The receiving server checks the signature against a public key in your DNS to confirm the message came from your domain and was not altered.
Read the definitionDKIM selector
A DKIM selector is a label in the DKIM signature that tells the receiving server which public key to fetch from DNS. It lets one domain publish several DKIM keys at once.
Read the definitionDMARC
DMARC (Domain-based Message Authentication, Reporting and Conformance) is a DNS record that tells receiving servers what to do with mail that fails SPF and DKIM checks for your domain, and where to send reports about it.
Read the definitionDMARC aggregate report
A DMARC aggregate report is a daily XML summary that a receiving mail provider sends you. It lists the servers that sent mail using your domain and whether each passed SPF, DKIM and DMARC.
Read the definitionDMARC alignment
DMARC alignment means the domain that passed SPF or DKIM matches the domain in the visible From address. A message passes DMARC only if at least one of the two passes and is aligned.
Read the definitionDMARC policy
A DMARC policy is the p= value in your DMARC record. It tells receiving servers what to do with mail that fails authentication: p=none takes no action, p=quarantine sends it to spam and p=reject refuses it.
Read the definitionEmail authentication
Email authentication is the set of DNS-based checks that let a receiving server confirm a message really came from the domain it claims. The core three are SPF, DKIM and DMARC.
Read the definitionMAIL FROM domain
The MAIL FROM domain is the domain in the envelope sender of an email, also called the Return-Path. Setting a custom one in Amazon SES makes SPF align with your From domain, which DMARC needs.
Read the definitionSPF
SPF (Sender Policy Framework) is a DNS record that lists which servers may send email for a domain. Receiving servers check the sending server against that list and treat mail from anywhere else as suspect.
Read the definitionSPF flattening
SPF flattening replaces the include entries in an SPF record with the IP addresses they resolve to, so the record needs fewer DNS lookups and stays under the limit of 10.
Read the definitionReputation and deliverability
How mailbox providers decide where your mail lands, and how to read their signals.
Blocklist
An email blocklist is a list of IP addresses and domains known or suspected to send spam. Receiving servers consult these lists and may reject or filter mail from anything on them.
Read the definitionEmail deliverability
Email deliverability is your ability to get messages into the recipient's inbox rather than the spam folder or nowhere at all. It is different from delivery, which only means the receiving server accepted the message.
Read the definitionGoogle Postmaster Tools
Google Postmaster Tools is a free service that shows how Gmail sees the mail you send to its users: spam rate, reputation, authentication results and delivery errors for a domain you have verified.
Read the definitionIP reputation
IP reputation is how mailbox providers rate the IP address your mail is sent from, based on the bounces, complaints and spam reports tied to it. On a shared IP you share that rating with other senders.
Read the definitionSender reputation
Sender reputation is the standing mailbox providers assign to your sending domain and IP addresses, based on your history of bounces, complaints, engagement and authentication. It decides whether your mail reaches the inbox.
Read the definitionAmazon SES
The parts of SES that decide what you can send, to whom, and what you get told.
Amazon SES
Amazon SES (Simple Email Service) is the email sending service from AWS. You send mail through its API or SMTP, pay per message, and SES handles delivery. It gives you infrastructure and raw events, but little monitoring.
Read the definitionCloudWatch alarms for SES
CloudWatch alarms for SES watch metrics such as the account bounce and complaint rates and notify you, usually through an SNS topic, when a value crosses a threshold you set.
Read the definitionConfiguration set
An Amazon SES configuration set is a named group of rules applied to the mail you send with it. Its most common use is event publishing: sending bounce, complaint, delivery, open and click events to a destination such as an SNS topic.
Read the definitionDedicated IP
A dedicated IP is an IP address that only you send email from. Its reputation depends entirely on your own sending, which gives you control and removes the influence of other senders.
Read the definitionIP warm-up
IP warm-up is the practice of raising your sending volume gradually on a new IP address, so mailbox providers see steady, wanted mail and learn to trust it before you send at full volume.
Read the definitionSES account review
An Amazon SES account is under review when AWS has found its bounce or complaint rate too high. AWS gives you time to fix it, and can pause sending if the rates keep climbing or reach its higher limits.
Read the definitionSES sandbox
The Amazon SES sandbox is the restricted mode every new account starts in. You can send only to verified addresses and domains, up to 200 messages per day and one message per second, until AWS grants production access.
Read the definitionSES sending limits
Amazon SES sending limits cap how many emails you can send in a rolling 24 hours (the sending quota) and how many per second (the maximum send rate). They apply per region and count recipients, not messages.
Read the definitionVirtual Deliverability Manager
Virtual Deliverability Manager (VDM) is a paid Amazon SES feature that adds deliverability dashboards, ISP-level metrics and recommendations inside the AWS console. It shows how your mail is doing, but it does not alert you.
Read the definitionMonitoring
Watching all of the above so you hear about a problem before AWS does.
DMARC monitoring
DMARC monitoring is watching your DMARC setup so you know when it breaks or when someone abuses your domain. It has two parts: checking that your DMARC record is present and sound, and analysing the reports receivers send you.
Read the definitionDNS monitoring for email
DNS monitoring for email watches the records that authenticate your mail, SPF, DKIM, DMARC, BIMI and MAIL FROM, and alerts you when one is changed, removed or broken, before it hurts delivery.
Read the definitionEmail deliverability monitoring
Email deliverability monitoring is the ongoing tracking of the signals that decide whether your mail reaches the inbox: bounce and complaint rates, authentication records, suppressions, volume and reputation. Its job is to warn you early.
Read the definitionAll terms, A to Z
D
E
S
- Sender reputationReputation and deliverability
- SES account reviewAmazon SES
- SES sandboxAmazon SES
- SES sending limitsAmazon SES
- SMTP error codesBounces and complaints
- Soft bounceBounces and complaints
- Spam trapBounces and complaints
- SPFAuthentication
- SPF flatteningAuthentication
- Suppression listBounces and complaints
Know before AWS does
SendScope watches the rates, records and lists in this glossary for your SES account and tells you the moment one drifts. Free for one account.