Frequently Asked Question
Building and maintaining a clean, well-segmented email list is essential for successful email marketing. A CSV (Comma‑Separated Values) import is one of the most efficient methods — it allows bulk uploads, custom mapping, and smart filtering. In this comprehensive guide, you'll learn how to:
Properly format your CSV file
Use Mailer Rocket’s CSV import feature
Troubleshoot common CSV issues
Implement best practices for list health and segmentation
Ready to elevate your email marketing? Let’s dive in.
1. What is a CSV File—and Why Use It?
A CSV is a simple, text-based spreadsheet format where each line corresponds to a record, and commas separate fields. You can export it from tools like Excel, Google Sheets, or CRM platforms, making it a universal and accessible format.
Why choose CSV for import?
Bulk management: Upload thousands of contacts at once
Custom fields: Map data like city, tags, preferences, etc.
Flexibility: Import into any ESP or CRM system
Mailer Rocket supports CSV import as a standard, user-friendly method to add new or update existing contacts—complete with field mapping and duplicate checking
2. Preparing Your CSV File
A well-prepared CSV ensures a smooth import and clean dataset. Follow these steps:
a. Use Proper Formatting & Encoding
UTF-8 encoding prevents character corruption—crucial for international data
Keep no extra sheets—everything should be in one table
Avoid blank rows and trailing spaces around values
b. Clean & Segment Contacts
Remove duplicates, manually or with dedupe tools
Check for invalid emails (e.g., missing "@")
Consider tagging columns—like “newsletter”, “VIP”, or custom interest labels
c. Set Column Headers
These will be mapped during Mailer Rocket import for seamless integration.
3. Step-by-Step: CSV Import in Mailer Rocket
Mailer Rocket’s CSV import tool is built for simplicity and efficiency. Here's a detailed walkthrough:
Step 1: Access the Import Tool
Log in at MailerRocket.com
Navigate to Contacts > Import and select “Import from CSV”
Step 2: Upload the CSV
Drag & drop or browse to select the file
Step 3: Map Your Fields
A visual interface prompts you to map each CSV column to your MailerRocket fields:
| CSV Column | Map To |
|---|---|
| Email (required) | |
| First Name | First Name |
| City | Custom Field |
| Tags | Tags |
Skip any unnecessary columns
Create new custom fields as needed
Step 4: Import & Validate
Click “Import” after mapping
Mailer Rocket processes the file, removes duplicates, and flags invalid or banned addresses.
You’ll receive a report detailing:
Number of contacts added
Duplicates skipped
Errors and invalid entries logged
Step 5: Post-Import Actions
Contacts are tagged and segmented based on your CSV
Confirm import fields and run a short welcome or onboarding automation
4. Common CSV Import Issues & Solutions
Despite best efforts, errors can occur—here are common pitfalls and how to resolve them:
✖ Encoding Errors
Non-English characters may break formatting. Save your file in UTF-8 encoding and re-upload
✖ Misaligned Columns
If headers don’t map correctly, set the correct field or mark the column as “Skip.”
✖ Invalid or Role‑Based Emails
MailerRocket—like most ESPs—will block addresses like admin@company.com or invalid formats “abc@”. Those entries will be flagged in the import log
✖ Duplicate Contacts
Duplicates are automatically removed—only the latest or most complete entry is kept
✖ Missing Required Fields
Ensure the Email column is present and correctly labeled; otherwise, validate before uploading.
5. Best Practices for Clean, Engaged Lists
CSV import is powerful, but responsible list management ensures stronger engagement:
- Use Opt-In
Confirm that all imported contacts have explicitly opted-in. CSV import doesn't manage opt-in—so compliance (e.g., GDPR) relies on your process.
- Tag During Import
Leverage tags like newsletter, VIP, or webinar2025 for post-import segmentation and automation.
- Verify Email Health
Clean lists reduce bounce rates. Tools like MailerRocket’s integration for validation help protect sender reputation.
- Automate Follow-Ups
Use MailerRocket's workflows to trigger welcome series for newly imported CSV contacts.
- Maintain Regular Hygiene
Re-import CSVs periodically (e.g., monthly) to update outdated information and remove inactive users.
6. Why Mailer Rocket Makes CSV Import Easy
MailerRocket simplifies CSV imports with:
Intuitive UI: Easy drag‑and‑drop and field mapping
Smart hygiene: Auto‑dedupe, invalid email detection, and banned-address filtering.
Automation integration: Imported contacts can trigger workflows
Comprehensive logs: Clear import summary with results and errors
In fact, Mailer Rocket’s blog highlights that the platform provides clear CSV formatting instructions and ensures a smooth import experience.
Conclusion
Importing contacts via CSV is a versatile, powerful tool that fuels your email marketing—when done right. With MailerRocket.com, the process is efficient and built for success:
Flexible field mapping and real-time validation
Automated hygiene like duplicates and invalid emails
Full integration with tagging and workflows
By following this guide, you’ll be able to build and segment your audience effectively, maintain list integrity, and launch targeted campaigns seamlessly.