DKIM Replay: Why a Valid Signature Doesn't Prove the Sender
A DKIM replay attack re-sends one validly signed message to millions and it still passes. How replay works, a safe lab to see it, and how DKIM2 fixes it.
Postbox Consultancy Services
Land Your Emails in the Inbox. Every Time.
Expert AI Email Deliverability Consulting for Growth-Focused Businesses
Transform your email deliverability with cutting-edge AI technology and expert consultation. We ensure your messages reach the inbox, not spam folders.
500+
Clients Served
100M+
Emails Delivered
Our Values
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Postbox Consultancy Services follows the universal values of Truthfulness, Compassion and Tolerance.
Our Services
Comprehensive Email Deliverability Solutions
From audits to full infrastructure management, we provide end-to-end email deliverability services powered by AI and industry expertise.
Email Deliverability
Landing in spam, open rates sliding, or blacklisted? Diagnose it, fix it, and keep it fixed.
Learn MoreEmail Infrastructure & Tools
The plumbing done right: authentication, sending domains, warmup, and the platform behind it all.
- SPF / DKIM / DMARC / BIMI setup
- Large-scale sending platforms & mail servers
- ESP and tool implementation
- Campaign management & team training
Cold B2B Email
Outbound that reaches inboxes and books meetings - infrastructure, lists, copy and sending, done safely.
- Cold-safe sending infrastructure
- Domain & mailbox setup, warmup
- List building & cleaning
- Campaign setup & deliverability care
Email Team as a Service (ETaaS)
Your entire email operation - strategy, builds, sending, monitoring - run by our team on retainer.
- Dedicated email team, fraction of the cost
- Campaigns + infrastructure + reporting
- Ongoing monitoring & optimization
- 10+ years, 500+ businesses
Trusted by Businesses Like Yours
Testimonials
"Working with Sandeep at Postbox Services is a pleasure. He is a consummate professional who truly knows his craft. Highly recommended for any email deliverability challenge."
"Postbox Consultancy Services conducted an email deliverability audit for us and the results were outstanding. Detailed, actionable, and delivered on time."
"Sandeep and his Postbox Services team know their way around email deliverability better than anyone we have worked with. A genuine expert."
"Sandeep is seriously a genius. Fast response time, understood the problem immediately, and fixed issues that had been hurting us for months."
"Postbox Consultancy Services is extremely helpful in reaching out to the right audience. Our open rates improved significantly after their audit."
"Working with Sandeep at Postbox Services is a pleasure. He is a consummate professional who truly knows his craft. Highly recommended for any email deliverability challenge."
"Postbox Consultancy Services conducted an email deliverability audit for us and the results were outstanding. Detailed, actionable, and delivered on time."
"Sandeep and his Postbox Services team know their way around email deliverability better than anyone we have worked with. A genuine expert."
"Sandeep is seriously a genius. Fast response time, understood the problem immediately, and fixed issues that had been hurting us for months."
"Postbox Consultancy Services is extremely helpful in reaching out to the right audience. Our open rates improved significantly after their audit."
FAQs
My open rates are continuously going down and my emails land in spam. How can you help?
Delivery problems stem from various factors that require proper analysis. An email deliverability audit identifies the underlying issues - authentication gaps, reputation problems, content triggers, or infrastructure faults - and gives you a prioritised fix list.
Can Postbox Services provide us consultancy while we do our own stuff?
Yes. We work as external consultants or auditors, assisting your internal teams in managing email delivery themselves. We train, advise, and review without needing to take over your operations.
What is the best open/click rate Postbox Services assure?
Rates depend on your list quality, industry, content, and sending history. No honest consultant guarantees specific numbers. What we guarantee is a thorough audit, actionable recommendations, and measurable improvement in deliverability metrics.
We are looking to build email infrastructure which can handle few million emails daily. Can Postbox Services help?
Yes. We design and build sending systems at any scale - from startup outreach setups to enterprise-grade platforms handling tens of millions of messages per day.
Where can I host my email infrastructure?
It depends on your volume, compliance requirements, and budget. We evaluate options including AWS SES, dedicated SMTP providers, self-hosted MTAs, and hybrid setups - and recommend the right fit for your specific situation.
From the Blog
What Is a DMARC Aggregate Report? (And How to Actually Read One)
A provider dropped an unreadable XML file in your inbox? Here is what a DMARC aggregate report is and how to read one, field by field, with a worked example.
How to Read Email Headers to Spot Phishing and Spoofing
Anyone can fake a sender name - the email headers are the receipts. Learn to read Authentication-Results and the Received chain to catch a spoof in seconds.
What Is TLS-RPT? How to Set Up MTA-STS Safely (Step by Step)
TLS-RPT tells you when senders cannot reach your mail server securely. Learn how it works, what the reports mean, and the safe order to set up MTA-STS without breaking your email.