Mail Relay

• 1: Overview
• 2: Announcements
• 3: Email and DNS
• 4: FAQ
• 5: Getting started

1 - Overview

The Elastx Mail Relay service facilitates sending large numbers of emails and is especially suited for applications/services that needs to send emails.

The scope of the service is access to our SMTP server for sending emails.

To use the service you must configure the necessary DNS records on the domain names you wish to use as sender address for your emails.

2 - Announcements

2025-01-08 DKIM signing now required for all mail relay customers

Breaking changes

All mail relay customers are now required to implement DKIM signing for the domains they wish to use with our mail relay service. This can be as simple as adding a DNS record, please contact our support to get started. From 2025-04-01 our Mail Relay service will reject mails from domains without DKIM configured.

Background

Forged addresses and content are widely used in spam, phishing and other email frauds. To protect legitimate organisations and end users, more and more email providers are starting to reject mail sent without a valid DKIM signature.

DKIM adds a digital signature to an outgoing message. The receiver can, using this digital signature, verify that an email coming from a specific domain was indeed authorized by the owner of that domain. Usually this verification is done automatically by the receiving mail server and is transparent to end-users.

Impact

From 2025-04-01 we will not accept sender domains without DKIM configured.

If you are already using our DKIM signing service there is no action needed. If you have any questions or want to set up DKIM signing for your domains, please register a support ticket at https://support.elastx.se/.

2024-05-01 DKIM signing service now available

We now offer DKIM signing on emails sent through our mail relay.

What’s new?

Previously the only option for DKIM signed messages sent through our mail relay was to sign the emails before sending them to us. This is still a viable option in case you want to control the key used for signing. As an alternative to the above, you can now contact us to request that Elastx mail relay handles DKIM signing for you.

Background

DKIM adds a digital signature to an outgoing message. Receiving mail servers can, using this digital signature, verify that a message did originate from a trusted source for the sender domain.

Spam and phishing attempts are such a big problem in the industry today that unsigned emails are much more likely to be marked as spam, subject to heavy rate-limits, and/or outright refused on the receiving end.

Impact

There is no impact if you already sign your messages before sending them to our mail relay.

We heavily recommend all customers not already signing their messages, to use our DKIM signing. All mail sent through our mail relay service will be forced to carry a DKIM signature at a future unenclosed date.

If you have any general questions or would like to sign-up please contact us at hello@elastx.se. For any technical questions please register a support ticket at https://support.elastx.se.

3 - Email and DNS

DNS plays a vital role in regards to email, there are three types of DNS records that are essential to ensuring your emails reach the recipients without being flagged as spam:

Additional reading

External resources that explains how DMARC, DKIM and SPF works:

• Cloudflare - What is a DNS DMARC record?
• Cloudflare - What is a DNS DKIM record?
• Cloudflare - What is a DNS SPF record?

4 - FAQ

Price?

Please see the website.

How many emails can I send?

We recommend a maximum rate of 10 emails per second.

Multiple user accounts?

Yes, a couple of user accounts are fine.

5 - Getting started

Overview

In short the required steps are:

1. Contact the Elastx Support to get user account and password for the SMTP server
2. For each domain you want to send emails from:
   1. Create DNS record for Elastx challenge token (for each user account)
   2. Create DNS SPF record
   3. Create DNS DKIM record
   4. Create DNS DMARC record

Once these steps are completed you can use our SMTP server to send emails.

If you are unfamiliar with SPF, DKIM and DMARC please see this article.

Terminology and general info

Please keep in mind that when you create a DNS record for the Elastx challenge token, that user account will be allowed to send emails with any sender address for the domain name.

DNS records

If you use multiple sender domains all domain names will need the below DNS records configured.

Example: You are using sender addresses tom@example.com and alice@example.se - this means the below domain names will need to be configured with the correct DNS records:

• example.com
• example.se

Elastx Challenge token

This record authorizes a user account to use the domain as sender address for emails.

Each user account will need a record for each domain they should be allowed to use as sender address.

The record is created as a TXT record directly under the sender domain name - ie. domain.com.

A simple DNS lookup should return something like:

$ dig +short domain.com TXT  
"elastx-mrs=f7ee5ec7312165148b69fcca1d29075b14b8aef0b5048a332b18b88d09069fb7"  
(..)

To generate the value of the elastx-mrs record, take the SHA256 sum of your user account email address:

echo "elastx-mrs=$(echo -n "user@domain.com" | sha256sum | cut -d ' ' -f 1)"

Note that the address used above should be your user account, not your sender address.

SPF record

This record determines what email servers are allowed to use the domain name as sender address.

The record is a DNS TXT record for domain.com where domain.com is your sender address domain name.

A basic value that only allows Elastx email servers:

"v=spf1 include:elastx.email -all"

DKIM record

DNS TXT record should be created for elastx._domainkey.yourdomain.com with value as provided by Elastx. Replace yourdomain.com with your sender address domain name.

Due to the size of the record it will be split into multiple TXT records. Ie. a DNS lookup will show something similar to:

$ dig elastx._domainkey.yourdomain.com TXT
(..)
;; ANSWER SECTION:  
elastx._domainkey.yourdomain.com. 1800 IN    TXT     "v=DKIM1; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwHsOJDTnxAkcz/RBek0XDqLaSZov/icY7mZHUSIV7gbHRVLhMWKvWqDV56WdbO+tVo2  
Gaf298Jo0WxwGsIUe0zi6dT0WXgv2zhP0KDT5aRu4q34SsLvrDe218xOC677gm6xUcFaqIMeiU73b9osCDlAxnNSwa2pjxx9yeO6py75tfzw86YkKUvPXPUW754E6mu/k+/4q" "z4NeFnGrCyHLr5rlyxpljMyL8eD13VRP3am  
kCl3Bcgkzt/JWLLa3/9X+N8gkWbB1W2RHAxacvxErSN5K8UHOAT3cUR3qvPGjE4iIKLoU1IkH7s8Gud5gHkiiY5opgDhdfz2kiILyrSv5DQIDAQAB"
(..)

DMARC record

DNS TXT record should be created for _dmarc.yourdomain.com where yourdomain.com is your sender address domain name.

Elastx does not have any specific requirements for the value, it just needs to be a valid DMARC policy.

Example value:

v=DMARC1; p=quarantine; adkim=r; aspf=r;

SMTP server

Configure your application/service with the address to our SMTP server (below) and your user account + password.