Troubleshooting Common Mail Merge Errors

If your mail merge fails to send or displays errors, this guide helps you identify and resolve the most common issues — including CSV formatting errors, attachment failures, merge field problems, and link issues. Find the error you're experiencing below and follow the numbered fix steps.

Why Do I Get a "Mail merge couldn't be created" Error?

Problem: You receive a Mail merge couldn't be created error when attempting to send your campaign.

Solution: Your pre-header is longer than 130 characters. This often happens when the pre-header is generated using the AI generation tool, which can produce text that exceeds the limit. Shorten your pre-header text to 130 characters or fewer, then resend the campaign.

How Do I Fix CSV Formatting Errors?

Most mail merge send failures trace back to the CSV file. Match your error to one of the fixes below, correct the file, and upload it again. For full file requirements, click here.

Fix the "Incorrect CSV format, missing 'Email' header" Error

This error means ContactMonkey can't find an Email column — usually because of a header or separator problem.

1. Open the file and confirm the first column heading is exactly Email, with no spaces before or after it, and with a capital "E"
2. Confirm every column has a heading and that headings contain no special characters, numbers, or line breaks
3. Save the file as CSV UTF-8 (Comma delimited) (*.csv) — not Excel Workbook (.xlsx) or another CSV variant
4. On a device purchased in the EU, your file may use semicolons (;) instead of commas as separators. Replace the semicolons with commas using the steps here
5. Upload the corrected file again

Fix the "Invalid email addresses" or Special Character Error

If the error names specific recipients, the data in those rows is breaking the file.

1. Check that every email address has a complete domain (ends in .com, .org, etc.).
2. Remove spaces before or after email addresses. Use Excel's TRIM function to clear hidden spaces in bulk
3. Remove special characters and stray commas from the flagged rows
4. Remove duplicate email addresses: select the Email column, then click Data → Remove Duplicates in Excel
5. Save as CSV UTF-8 (Comma delimited) (*.csv) and upload again

Fix the "Merge fields have inappropriate values" Send Error

If you see We could not send your Mail Merges to the following emails. Please double-check that all merge fields have appropriate values, a column's data doesn't match the format ContactMonkey expects.

1. Format date columns (such as birthday) as YYYY-MM-DD.
2. Remove dashes, spaces, and other non-numeric characters from phone number columns
3. Delete any columns you aren't using as merge fields
4. Fill in blank cells in columns used as merge fields, or remove those rows
5. Resave the file as CSV UTF-8 (Comma delimited) (*.csv)

Note: Excel can silently reformat data when you reopen a CSV — for example, converting dates or stripping leading zeros. Make formatting fixes in one pass, save, and close Excel before uploading. Keep Excel closed while the upload runs.

Why Do Attachments Cause Send Failures?

Problem: Your mail merge fails when you include attachments.

Solution: Embed attachments directly in your email body.

Why Don't My SharePoint Links Work?

Problem: SharePoint links are too long, or recipients get "access denied" errors when clicking them.

Solution: Generate a share link in SharePoint instead of copying the URL from the browser address bar.

Why Are My Links Extremely Long with Security Information?

Problem: Your links start with URLs like https://yourcompany.safelinks.protection.outlook.com/.

Solution: You've copied a link that passed through your organization's security filtering (such as Microsoft SafeLinks). To get clean links:

1. Go directly to the source website instead of copying links from emails
2. Copy the URL from the address bar — it should be much shorter
3. Paste the clean link into your campaign

Example:
❌ Don't use: https://company.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcnn.com%2Farticle%3Fid%3D123... (long, modified URL)
✅ Use: https://cnn.com/article?id=123 (clean, original URL)

Why Does My Button Text Display Formatting Errors?

Problem: Your button displays unexpected characters or won't save properly.

Solution: Hidden formatting from copied text causes these errors. Type button text directly into the content block. If you must copy text:

1. Paste as plain text with Ctrl + Shift + V (Windows) or Command + Shift + V (Mac)
2. Alternatively, right-click and select Paste as plain text