Key Takeaways:

• Over-personalization reduces response faster than under-personalization in direct mail.
• The type of data used matters more than the volume of data used.
• The P.S. is still one of the highest-leverage personalization zones in direct mail.
• High-quality handwritten execution can double open rates in the right segments.
• Pre-canceled, commemorative, and foreign stamps routinely outperform indicia—when positioned correctly.

Most marketers think personalization in direct mail is binary. Either you use it—or you don’t.

That’s the mistake.

In direct mail, bad personalization performs worse than none at all.

Here are five field-tested rules that consistently separate high-response mail from wasted postage:

Rule #1: Control Personalization Density – More variables does not equal more response.

The fastest way to destroy credibility is to stack too many personalized elements into one letter.

It’s not natural

Common mistakes:
•   Name in the headline
•   Name again in the first sentence
•   City/state dropped mid-paragraph
•   Product history awkwardly injected
•   Over-specific references that break flow

What works better:
•   One or two personalization anchors per page
•   Placed where the eye naturally rests
•   Written so the copy still reads smoothly without the data

If removing the data makes the sentence feel broken, it was forced to begin with.

Rule #2: Personalize Signals of Relationship, Not Surveillance

Recognition beats precision.

High-response personalization signals relationship, not monitoring.

Data that works:
•   “You’ve been with us for over 5 years”
•   “Your last order was one of our most popular packages”
•   “Your previous contribution helped fund…”

Data that backfires:
•   Browsing behavior
•   Time-based tracking references
•   Over-granular product descriptions
•   Location references beyond city/state

The test:
If a prospect asks, “How do they know that?”, response drops.

If they think, “They remember me.”, response rises.

Rule #3: Weaponize the P.S.

Because the P.S. gets read even when the letter doesn’t.

Eye-tracking and response testing have proven this for decades:
The P.S. is one of the highest-attention zones in a direct mail letter.
It’s usually read first, before the letter itself.

High-performing P.S. personalization examples:
•   Prior gift amount with new suggested ask
•   Prior purchase with logical next step
•   Loyalty reference with urgency trigger

Execution detail:
•   Keep it short (1–3 lines)
•   Personalize only one element
•   Restate the core benefit or deadline

My favorite strategy is to reference something of great curiosity. For example, “The unique supplement I mentioned is flying off the shelf.”

Never waste the P.S. on boilerplate.

Rule #4: Use High-Quality Handwritten Personalization

High quality handwritten envelopes dramatically increase response… only when the segment justifies it—and then do it right.

This is not novelty handwriting.
And it is not cheap robotic scripting.

When we deploy handwritten execution, it’s typically for:
•   Top 10–20% donors or buyers
•   Reactivating lapsed high-value customers
•   Inner-circle or VIP segments
•   Strategic follow-ups, not first contact

What actually works:
•   Human-looking cursive or print
•   Natural variation in stroke and spacing
•   No repeated patterns across envelopes
•   Ink colors that mimic real pens (not blue-marker fake)

Inside the package:
•   A short handwritten note or
•   A Post-it note attached to a printed letter
•   With a believable reason someone took the time to write

This routinely lifts:
•   Open rates dramatically
•   Response rates meaningfully
•   Lifetime value over time

Yes, cost per piece rises.
Cost per response often drops.

Rule #5: Use Stamp Strategy as a Response Lever

Most marketers treat stamps as logistics and for direct mail use preprinted indicia instead..

But high-response mailers treat stamps as psychology.

What testing shows:
•   Precanceled stamps outperform indicia by 10–15%
•   They visually signal “real mail”
•   They change how recipients handle the envelope – and postal people.

A precanceled stamp doesn’t cost more, but it does increase response.

Also other advanced applications of stamps:
•   Commemorative stamps for donor or premium segments
•   Foreign stamps used strategically on bulk mail

These require:
•   Postal coordination
•   Correct positioning
•   Experience negotiating approvals

When done correctly, they outperform standard bulk mail—quietly and consistently.

Bottom Line for Direct Mail Marketers

Personalization doesn’t win because it’s clever.
It wins because it feels intentional.

When personalization:
•   Signals respect
•   Feels human
•   Matches the value of the prospect

Response follows.

When it feels automated or lazy, response collapses.

Action:
If your team wants to test advanced personalization—handwriting, premium packaging, or response-driven stamp strategies—this is where experienced execution matters. Get it right, and the economics work.

Email Michael at [email protected] or give him a call at 615-933-4647 to see how CDMG can help.

About Craig Huey:

Craig Huey is President of Creative Direct Marketing Group (CDMGinc.com), a 30-year leader in direct response advertising and multi-channel marketing. Under his leadership, CDMG has:

• Tested more than 10,000 digital marketing variables.
• Mailed over 10 million pieces of direct mail in the last year alone.
• Won more than 120 awards for marketing excellence.

Craig is also the publisher of Direct Marketing Update, the trusted newsletter for company presidents and marketing directors looking to maximize ROI with cutting-edge, accountable advertising strategies.