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 Sometimes it's an outdated SPF release, sometimes a DKIM key that was never rotated, sometimes a domain reputation that has quietly deteriorated over months, or simply a list full of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 – and 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 recommend.

Reviewed by humans

A consultant personally reviews every result before we send you 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 sending.

1. Upload

The email file is uploaded via 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. No 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:

The email file may contain personal data (sender, recipient, content). It is used exclusively for the analysis, treated as confidential, and deleted once the consultation is complete.

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.

Sending behavior

Irregular sending volumes, missing or incorrect IP/domain warm-up, inconsistent sender identity (From-name, From-address, reply-to).

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 consultation 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 in use.

3. Action plan

Concrete, prioritized steps: what comes first, what comes next, and the expected impact.

4. Ongoing support

If you'd like, we support you with implementation, including a follow-up check after 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
• Explicitly also: companies that aren't a Martrexo customer and don't need to become one

Trust
built over years of experience

M3AAWG member

Active in the global alliance against spam and abuse.

GDPR-compliant hosting in Germany

Real human support, no call centers.