When you import a list into MailChimp we'll scan your file for duplicates, bounces, and unsubscribes. If the system comes across an incorrect file format, an incomplete or malformed email address, or inconsistencies in the file, all or some of the email addresses may be blocked from import. Below, you'll learn about some issues that could cause the import to fail.

If you're importing a large list, it can take some time to complete the upload. Click the notification bubble on your Profile Name in the navigation to view the status of your import. When your import is complete, we'll send a confirmation message to the Account Owner's email address. You can also undo a list import for any reason.

In this article:

Problems importing the file

If you're seeing your file not upload into MailChimp at all, check the following for some possible causes to this issue:

Check the file type

If you chose the Upload from File option, make sure the file you are using is a tab-delimited text file or CSV file. The system is not designed to support imports of Excel (.xls), ACT!, .vcf (vCard), or other file types.

Switching ESPs

If you are switching from another ESP, the file that was exported may not be formatted in a way that MailChimp can read. Take a look at this article for info on how to format your import file. In addition, if you're switching over from Constant Contact and have more than 60 lists, you may see an error on the import. There is a limit to the number of lists that can be converted to Groups in MailChimp.


Importing an OPTIN_TIME or CONFIRM_TIME with a future date will cause a syntax error. Additionally, our system only looks at these fields the first time you import the subscriber. We won't change the times or check that field when a subscriber is being updated.

Syntax errors

If MailChimp comes across a malformed or incomplete email address, the system marks it as a syntax error and removes it from the import. We'll display the number of errors found on the list import page when the upload is completed. To view the report, click on the X emails had syntax errors link (where X is the number of errors found in your file). You can view all of the syntax errors we found in order to fix them manually and re-add them to your list.

If you navigate away from the initial import results, you can view the syntax errors in the MailChimp List Import Complete email we send to the administrator address on file for the account. In addition, you can visit the List Import page to view import history for this list which will mention any syntax errors as well. The upload details will be available to view in the account for about 24 hours. If you're seeing syntax errors for your import, check the common causes below:

Missing information

Make sure all the email addresses include the necessary information. For example, john@aol is missing the .com portion and john@aolcom is missing the period. Once the address has been corrected to john@aol.com it can be successfully uploaded to the system.

Spaces in the file

Make sure the email addresses don't contain beginning or trailing spaces. Some export utilities sometimes add invisible spaces in the middle of email addresses too. Extra spaces can result in an otherwise valid address being reported as a syntax error. If you do have spaces, the TRIM function in Excel can remove all spaces from text (except for single spaces between words). Consult the help documents for your version of Excel to learn how to use the TRIM function. Other spreadsheet programs may have similar functions as well.

Typos in the address

Check the file to see if there's a typo in the email address. We check for misspellings of common domains, such as gamil.com instead of gmail.com and prevent them from being added to your list. This helps keep your list free of bounces.

Results don't match the list subscriber count

You can visit the List Import History page for a full breakdown of the results. The upload details will be available to view in the account for about 24 hours.

If the numbers shown on the Import History page don't add up based on your total subscriber count, there are a few things to look for.

Was the Auto-Update My Existing List option enabled?

We'll add any new email addresses to your list as new subscribers. If an email address is already on your list, instead of completely skipping it as a duplicate, we'll check all the fields and update that subscriber's information. Updated subscribers won't increase your list size, but will be included in the number of emails added or updated. You can tell whether this option was enabled because the import results will display that email addresses were added or updated instead of just added. Check out this article for more information on reading the import history for a list.

Was an account upgrade triggered during the import?

If you reach the upper limit of your current monthly plan with an imported list, the import process will stop temporarily and trigger an account upgrade confirmation email. This email is sent to the contact address listed for the administrator for the account. Once the upgrade is confirmed, the import should restart.

When you refresh or return to the page, you may see a message about upgrade, and a red notification bubble next to your Profile name. If your user type allows you to access billing, you will see the option to Approve Upgrade.

If you see View Your List, you'll need to contact the list admin or owner to continue your import. To find the email address for the administrator of your account, follow these steps:

  1. Click your username to expand the Account Panel and click Account.
  2. Click the Account settings drop-down menu and choose Contact information.
  3. Look for the email address listed under Administrator.


MailChimp supports Unicode (UTF-8), ASCII, and extended ASCII characters. So when importing your list into MailChimp, make sure that the characters are all encoded as UTF-8 in order to prevent syntax errors from occurring.

This feature is limited to certain user levels. You can see your user level on the Users & Account Details page and this article explains what each level can access in the account.

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