Koltrix
Product
Adding Your Domain to Koltrix: The Five DNS Records
Koltrix asks for five DNS records: ownership, MX, SPF, DKIM and DMARC. What each one does, what its value looks like, and the order to publish them in.
5 min read
GuidesMX records explained: priorities, fallbacks and null MX
How sending servers pick among MX records, what preference values really do, what happens without an MX, and when to publish a null MX instead.
4 min read
DeliverabilitySPF, DKIM and DMARC in plain English
Three DNS records decide whether your email arrives. What each one actually does, what to publish, and the four mistakes that cause most of the support tickets.
4 min read
GuidesMoving from Google Workspace: the DNS cut-over checklist
The exact order of operations for moving a domain's email off Google Workspace without losing a single message, plus what Koltrix does not import yet.
2 min read
GuidesSending DMARC reports to another domain: the auth record
If your rua address lives on a different domain, receivers check an authorization record first. How the _report._dmarc record works and how to test it.
4 min read
GuidesMTA-STS from scratch: DNS record, policy file, testing
Set up MTA-STS for inbound mail: the _mta-sts TXT record, the HTTPS policy file, testing mode, then enforce, plus the mistakes that break delivery.
5 min read
GuidesTwo email providers on one domain without breaking auth
Running a workspace mailbox provider and a transactional sender on the same domain? Combine SPF, give each its own DKIM selector, and align DMARC.
5 min read
DeliverabilityCustom tracking domains and why shared link domains hurt
Click tracking rewrites links through a redirect domain. If that domain is shared, its reputation becomes yours. Set up a branded one with HTTPS.
4 min read
GuidesEvery DNS record a sending domain needs, in one table
A reference table of the DNS records a domain that sends email should have: MX, SPF, DKIM, DMARC, MTA-STS, TLS-RPT and BIMI, with syntax for each.
4 min read
- Deliverability
SPF flattening: when it helps and when it breaks mail
Flattening replaces includes with IP ranges to dodge the lookup limit. Here is how it works, why it rots, and safer alternatives like subdomains.
5 min read
GuidesPublishing a 2048-bit DKIM key when DNS splits strings
A 2048-bit DKIM public key exceeds the 255-character TXT string limit. How string splitting works, provider quirks, and how to verify the result.
4 min read
DeliverabilityThe SPF 10-lookup limit: how to count and get back under it
Which SPF mechanisms count toward the 10-lookup limit, how to audit your record by hand, and the safe ways to trim includes before you hit permerror.
5 min read