Excel Segmentation

Defensive Lists for Small-Scale Email Sends

Not everyone is sending millions of emails. Sometimes it’s hundreds of thousands, and sometimes all you have is Excel. Mistakes still bite. Here's my practical, slightly ugly approach.

1. Start Clean: Columns and Filters Matter

Never trust Sheet1. Check columns: email, first_name, status, unsubscribed, segment. Filter inactive/unsubscribed users first.

TL;DR: Filter → Status = Active AND Unsubscribed = 0

Because even a small list gets messy fast.

2. Data Validation: Catch Duplicates and Format Errors

Emails without @ or duplicates fail silently. Use formulas or conditional formatting:

=ISNUMBER(FIND("@", A2))    → Highlights invalid emails
=COUNTIF(A:A, A2) > 1       → Flags duplicates

Otherwise your personalization tokens in HubSpot (or AMPscript strings in SFMC) can break.

3. Nulls and Defaults

Sometimes segment cells are empty. Fix with IF formulas:

=IF(B2="", "Default Segment", B2)

Small lists are forgiving, but fallbacks here -webkit-text-fill-color help.

4. Safe "Joins" / Merges

When merging engagement or preference sheets, be defensive:

=IFERROR(VLOOKUP(A2, Engagement!A:B, 2, FALSE), "No Data")

Even small merges need validation.

5. Keep Metrics in Mind

Track invalid emails, unsubscribed, duplicates removed. COUNTIF, SUM formulas, pivot tables help. Reporting small errors early prevents disasters.

Lessons Learned

Excel can scale to hundreds of thousands if you defend your data
Filter early, check duplicates, handle blanks, validate merges
Ugly formulas are okay; clarity and safety beat polish
Habits here translate directly to SQL/SFMC when scaling

Ready to scale? Same defensive patterns work for millions in Salesforce Marketing Cloud: full story here.