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Transactional Email - Concepts

Reviewed on 22 April 2024

Aggregate report

An aggregate report (rua) is a periodic summary that provides data about a domain’s email authentication activity. It includes information such as the volume of emails received, the percentage of emails that pass or fail DMARC checks, and the sources of failed authentication.


Deliverability is the ability for an email to arrive in a recipient’s email inbox.

DKIM record

A Domain Keys Identified Mail (DKIM) record is an email security standard. It provides you with an encryption key and a digital signature that allows you to verify whether an email was altered.

DMARC record

DMARC stands for Domain-bassed Message Authentication Reporting and Conformance. It is an email authentication protocol that helps prevent email spoofing and phishing attacks by verifying that the sender’s domain is legitimate. DMARC builds upon two other email authentication protocols: SPF and DKIM. It allows domain owners to publish policies in their Domain Name System (DNS) records specifying how emails sent from their domain should be handled if they fail authentication checks.

DNS propagation

DNS propagation is the time a DNS change takes to be updated across the internet.


Scaleway uses flags to provide you with more information about your emails. Flags can let you know whether an email you have sent is considered a spam, for example. There are seven types of flags:

  • Greylisted: This means that your email has been slightly delayed by the recipient, to ensure that Scaleway is not sending spam.
  • Hard bounce: This means that a critical error occurred while sending the email. Find out more about hard bounces.
  • Mailbox full: This means that your email was not able to reach the recipient’s mailbox, because it is full.
  • Mailbox not found: This means that your email was not able to reach the recipient’s mailbox, because it does not exist.
  • Send before expiration: This indicates that you have requested to send your email before a specific date (defined by you), and that your email expires after that date. This is useful if you are sending an email containing a password renewal link, for example.
  • Soft bounce: This means that a non-critical error occurred while sending your email. Soft bounced emails are retried. Find out more about soft bounces.
  • Spam: This means that your email has been considered spam.

Forensic report

A forensic report or failure report (ruf), is a detailed record of an email message that has failed DMARC authentication. It includes the complete headers and body of the failed emails, details of the authentication checks performed, and any errors encountered.

Hard bounce

Hard bounce occurs when an email is sent to an invalid email address or an address that does not exist. Unlike soft bounce, which is a temporary error, hard bounce is a permanent error.

In this case, most emailing solutions will blacklist these email addresses.

IP warming

IP warming is the process of gradually increasing the volume of emails sent through a new IP or an API that has not been used in a while.

The process of warming up an IP address consists of gradually sending emails from it, starting with small volumes and increasing the volume over a period of days weeks or months, according to a set schedule.

Internet service providers are wary of emails sent from new IP addresses with no reputation, so warming up an IP allows for better email deliverability and thus, better reputation.

IP reputation

IP reputation measures the trustworthiness of an IP address and the amount of unwanted requests it sends. An IP address that sends authentic, spam-free emails, earns a good IP reputation. An IP address that sends high amounts of spam or viruses earns a bad IP reputation. IP reputation allows you to reject requests that are coming from an IP address with a bad reputation.

MX record

A mail exchanger (MX) record is a DNS record that is required to deliver emails to your address. An MX record indicates which mail servers accept incoming emails for your domain and where emails sent to your domain should be routed to.

Scaleway provides its own MX server to improve email deliverability. However, Scaleway’s MX server is a blackhole. This means that any email sent back to it, will be lost with no possibility of recovery. If you have no MX server, we recommend you use Scaleway’s blackhole MX to avoid getting your emails rejected.


A preheader is the summary text that appears after the subject line when viewing an email in your mailbox.

Pristine spam trap

Pristine spam traps are email addresses created by Internet Service Providers (ISPs) and other entities, such as blacklist organizations, email providers or security companies, to monitor and track spam activity. As these addresses have never actually been used, they lack any history or reputation, making them ideal for generating spam reports.

Scaleway provides its own MX server to improve email deliverability. However, Scaleway’s MX server is a blackhole. This means that any email sent back to it, will be lost with no possibility of recovery. If you have no MX server, we recommend you use Scaleway’s blackhole MX to avoid getting your emails rejected.


Each MX record has a priority, or a number to designate the order in which your domain’s incoming mail servers receive your emails. The MX record with the lowest number is the first, or primary mail server to which outgoing mail servers attempt to deliver your emails.


Realtime Blackhole Lists are directories containing lists of IP addresses, domain names, and mail servers known to actively host, produce, send and/or forward spam or spam sources. Your emails will automatically be considered spam if you send them from an IP address, a domain name, or a mail server known to RBLs.

Recycled spam trap

Recycled spam traps are old domain registrations or email addresses that were once valid, but are no longer used by a company or an individual.


Repeatedly sending emails to these addresses will gradually harm your sending reputation. Make sure you clean your contact list often and that there are no spelling mistakes in the email addresses you are sending emails to.

Reputation score

A domain’s reputation score is similar to a grade that email providers give to your domain’s online reputation. The reputation score helps them decide whether the emails sent from your domain are trustworthy and should be delivered to your recipient’s mailbox, or if your emails should be blocked, classified as spam and rejected. Email providers calculate your domain reputation on a scale of 0 to 100.

The closer to 100 your reputation score is, the more receiving email servers will trust your emails. A high domain reputation score means better chances of your emails reaching the intended recipients’ mailboxes, while a low score might lead to emails being marked as spam or rejected.


A domain’s reputation score is determined by email providers and Internet Service Providers (ISPs), which means you have a different domain reputation for each email service provider.

Send API

A send API is the main API that is used to send transactional emails to recipients.

SMTP relay

An SMTP relay is a service or server that helps in the transmission of email messages from one email server to another. They act as a bridge between the sender’s mail server and the recipient’s mail server. SMTP relays are designed to handle large volumes of emails, ensuring that emails reach the recipient’s server more efficiently and reliably, without being flagged as spam.

Soft bounce

Soft bounce occurs when your email has been sent to a valid email address, and has reached the recipient’s mail server but your email could not be delivered for multiple reasons:

  • The recipient’s mailbox has exceeded its storage limit
  • The recipient’s mail server is down
  • The message was too large for the recipient’s mailbox

When a soft bounce occurs, the email software will try to resend the email for 72 hours (maximum) until the message is finally delivered.

Spam trap

Spam traps are email addresses that Internet Service Providers (ISPs) and blocklist operators use to detect and blacklist spammers and senders who fail to adhere to email best practices. These email addresses may look like legitimate email addresses, but they are not operated by real users. There are two types or spam traps:

  • pristine spam traps and
  • recycled spam traps.

Any contact that has not engaged by opening or clicking a link sent within an email from you in the past year might be a spam trap.


Make sure you regularly clean up your contact lists to avoid spam traps.

SPF record

An SPF record specifies the mail servers that are allowed to send email for your domain. It allows you to protect senders and recipients from spam and phishing attacks. SPF also prevents spammers from sending emails on behalf of your domain.

Transactional Email

Transactional Email is a platform that allows you to send transactional emails. Unlike marketing emails (which are mass distributions of the same marketing message to multiple recipients), transactional emails are personalized emails sent to individuals in response to events they have triggered (e.g. password recovery, billing information, delivery updates, etc).

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