Prerequisites
- Choosing Your Sending Domain — The domain choice is not easily reversed
Set Up Your Sending Domain
From an empty Mail Delivery Settings screen to a domain that can send.
Before You Begin
- Access to your domain's DNS records, at your registrar or DNS host. You cannot complete setup without it.
- A sending domain chosen in advance — the decision is not easily reversed
- The correct brand selected in Zyntro. Mail delivery is configured per brand.
Setup has two halves, separated by a gate. First you publish two records that prove the domain is yours to use, which unlocks Continue. Then Zyntro provisions the sending infrastructure and gives you three more records, which unlock Activate Setup.
Expect to move between Zyntro and your DNS host as you go, and expect to wait. DNS changes are not instant: they usually appear within minutes but can take up to 24 hours. Nothing is lost if you stop and come back — your progress is saved, and the screen resumes where you left off.
Steps
Open Mail Delivery Settings
Go to Communication > Email > Senders. On a brand with no sending domain yet, the screen explains that you will need DNS access and offers one button. Select I Understand, Let's Begin Setup.
Enter your sending domain
Type it into Sending Domain — for example comms.example.com. As you type, Return Path Domain fills in automatically as inbound. plus what you entered. Leave it as it is unless you have a reason not to; it must remain on the same registered domain as your sending domain.
Publish the MX record on your sending domain
In your DNS host, create an MX record:
- Hostname: your sending domain, for example
comms.example.com - Value:
inbound.postmarkapp.com - Priority:
10
This routes mail addressed to your sending domain into Zyntro, which is how replies reach the platform. The hostname and value are shown on screen with copy buttons.
Publish the CNAME record on your return path domain
Create a CNAME record:
- Hostname: your return path domain, for example
inbound.comms.example.com - Value:
pm.mtasv.net
This is where bounce reports are collected, so Zyntro knows which addresses failed and why.
Tick each record to check it
Tick I have created the MX record and I have created the CNAME record. Ticking is what triggers the check — Zyntro looks the record up in live DNS straight away and reports what it found.
If a record is not found yet, the tick clears itself and a Verify Again option appears. That usually means DNS has not finished propagating. Wait, then try again.
Select Continue
Continue unlocks only when both records have been found. Zyntro then provisions the sending infrastructure for your brand and creates the sending domain, which takes a few seconds.
Publish the DKIM record
Zyntro now shows a TXT record for DKIM, which signs your outgoing mail so recipients can confirm it was not altered or forged. The hostname and value are unique to your domain, so copy them from the screen rather than from anywhere else.
Create the TXT record at your DNS host, then tick I have Setup the DKIM records correctly to check it.
Publish the SPF record
Next is a TXT record for SPF, which lists who is allowed to send mail for your domain. Copy the value from the screen — it includes spf.mtasv.net, which authorises Zyntro's sending infrastructure.
If your sending domain already has an SPF record, do not add a second one. A domain may only have one, and two is treated as a misconfiguration. Merge the include: into the record you already have.
Publish your DMARC policy
Finally, Zyntro asks for a DMARC policy, which tells inbox providers what to do with mail that fails the DKIM and SPF checks. Unlike the others, the content is yours to decide. The screen shows the hostname to use — _dmarc on your registered domain.
If you have no policy yet, v=DMARC1; p=none; is the right place to start: it asks for no action and lets you begin safely. Tick I have Setup the DMARC records correctly once it is published.
Select Activate Setup
Activate Setup unlocks once DKIM, SPF and DMARC have all been found. Zyntro asks the delivery service to accept DKIM, SPF and the return path, then reloads the page as the DNS Verification dashboard.
Result
Your brand has a verified sending domain, and Mail Delivery Settings now shows a card for each record rather than the wizard.
Check that each of DKIM, SPF and Return Path reads Accepted for sending, not just Published in DNS. Publication is your side of the work; acceptance is the delivery service's, and it is the one that decides whether mail actually goes out. If anything is still only published, select Verify All Records — and if it was published moments ago, give it time first.
You will also find your brand's dedicated mailbox address at the bottom of the page, which is how inbound mail reaches FLOW.
Troubleshooting
It unlocks only when both the MX and CNAME records have been found in live DNS. Re-tick each box to run the check again, and read the message underneath — it says which record is missing. Newly created records can take up to 24 hours to appear.
Check for a duplicated domain in the hostname. Many DNS hosts add the domain for you, so entering comms.example.com as the hostname can produce comms.example.com.example.com. Compare what your DNS host shows against the value on the Zyntro card.
Setup stopped between the two halves, and the screen now offers Configure Sending Domain to resume. Nothing is lost. Select it and re-enter your sending domain.
There is a TXT record at the _dmarc hostname, but its contents are not a DMARC policy — often an SPF value pasted into the wrong record. A policy must begin v=DMARC1; and set a policy such as p=none. See Set a DMARC Policy.
