Email Deliverability Consulting
Vendor-independent consulting on email deliverability
Emails landing in spam, declining open rates, postmaster tools sounding the alarm, and often it's unclear what's really behind it. We'll take a look at your deliverability issues, independent of the sending system you use.
The cause is rarely where you look first.
A declining delivery rate almost never has a single cause. Sometimes it's an outdated SPF release, sometimes a DKIM key that was never rotated, sometimes a domain reputation that has quietly deteriorated over months, or simply a list full of inactive addresses. Most providers only analyze what's visible on their own platform. We look at the whole picture: DNS, authentication, sending behavior, content, list quality, plus what the major mailbox providers actually require right now.
Open. Vendor-independent.
Nothing is off-limits.
We run our own email gateways, so we know how deliverability works technically. That experience feeds into every analysis, regardless of the sending system used. Domain, setup and sending are analyzed exactly as they are. If the solution lies in a DNS correction, a change to the existing ESP, or a cleaned-up recipient list, that's exactly what we will recommend.
Vendor-independent
The analysis applies to your specific domain and sending, not to any particular tool or platform.
Transparent
Diagnosis, raw data and reasoning are all fully disclosed in detail, rather than just as a traffic light.
Reviewed by humans
A consultant personally reviews every result before we send you our feedback.
The fastest path to an initial diagnosis: one email.
A single email (EML, HTML, etc.) is enough, straight out of Outlook, Gmail, Apple Mail, or any other client. That one file already reveals a great deal: the complete delivery path, the authentication chain, technical anomalies in the sending process.
1. Upload
The email file is uploaded using the form on this page. Encrypted, confidential, GDPR-compliant.
2. Automated pre-check
The system reads the headers: SPF, DKIM and DMARC result and alignment, sender and routing information, anomalies in the delivery chain.
3. Human review
A deliverability consultant reviews the result and puts it in the context of your industry and sending volume. You won't just get an automatically generated score without context.
4. Feedback
The result is a clear, well-founded assessment with concrete, prioritized recommendations for action, sent by email.
Privacy notice:
Your email file may contain personal data (sender, recipient, content). It is used exclusively for analysis, treated as confidential, and deleted once the consultation process has been completed.
What we actually look at.
Our in-depth deliverability audits go further. Alongside the purely technical checks, factors like reputation and list quality are decisive for delivery.
Authentication
SPF, DKIM, DMARC (incl. policy level: none/quarantine/reject) and BIMI. DNS errors such as too many SPF lookups, expired or never-rotated DKIM keys, missing alignment between From-domain and signature.
Reputation & blocklists
Domain and IP reputation, listings with Spamhaus, SORBS, Barracuda, UCEPROTECT & co., analysis of Google Postmaster Tools and Microsoft SNDS.
Sending behavior
Irregular sending volumes, missing or incorrect IP/domain warm-up, inconsistent sender identity (From-name, From-address, reply-to).
List quality
Bounce rates, spamtraps, stale contacts, role-based mailboxes (info@, sales@) in the marketing list, engagement history.
Content & technical delivery signals
One-click unsubscribe (List-Unsubscribe header, RFC 8058), TLS encryption in transit, spam triggers in subject and content, text-to-image ratio.
Bulk sender requirements 2026
Checked against the current requirements from Google, Yahoo and Microsoft: mandatory authentication, complaint rates below 0.3% (target below 0.1%), mandatory one-click unsubscribe, unsubscribe requests processed within 2 days.
How our consulting service works
1. Initial check
Email upload, automated pre-check, initial personal assessment.
2. In-depth analysis
If needed, a full review of DNS, sending infrastructure, list quality and the postmaster data of the provider being used.
3. Action plan
Concrete, prioritized steps: what comes first, what comes next, and the expected impact.
4. Ongoing support
Upon your request, we'll support you with implementation, including a follow-up check after making the changes.
Who this is for
- Companies whose delivery rates are declining for no obvious reason
- IT and marketing teams who want a second, independent opinion on their existing setup
- Companies ahead of an ESP switch who want to clear up reputation baggage beforehand
- And, expressly so: Companies that aren't martrexo customers and don't see a need to be!
Trust
built on years of experience
CSA Certified
Whitelisted on the Certified IP List.
M3AAWG member
Active in the global alliance against spam and abuse.
BSI Hall of Fame
Gold status in the Email Security Year.
GDPR-compliant hosting in Germany
Real human support, no call centers.
FAQ
Do I have to become a martrexo customer?
No. The consultation applies to the domain and sending process in question, independent of the system behind it.
What will happen to the email we uploaded?
It will be processed exclusively for the purposes of our analysis in a GDPR-compliant manner; it will be deleted once the consultation has been completed.
Is the initial analysis really free?
Yes. The initial assessment based on the submitted email is free and non-binding.
What if the problem isn't technical at all?
Then we'll say so. Sometimes the cause lies in list quality or content, not in the technology; we'll assess those too.
Latency, reputation, blocklist signals
Delivery latency, reputation history and blocklist signals are tracked live as continuous telemetry at the frontend instead of grepping through log servers.