Troubleshooting Contact Imports

Each time you import contacts in Mailchimp, we look for duplicates, bounces, and unsubscribes, as well as incorrect file formats and syntax errors. These issues can prevent some contacts from being added to your audience.

In this article, you'll learn more about possible problems with your contact import.


Was my import successful?

After you import contacts, we recommend you take a look at the results on your Import History page. The Import History page includes details on any errors we found, and tells you which email addresses to review for issues to troubleshoot. These details remain on the Import History page for 24 hours.

To learn more about your import results and how to find them, check out View Your Contact Import Results.

Mailchimp won’t accept my file

If Mailchimp won't accept your file at all, there are a few possible causes.

  • The file type is unsupported.
    If you choose the Import from a CSV or tab-delimited text file option, make sure the file you upload is one of those two formats. The system does not support Excel (.xls), ACT!, .vcf (vCard), or other file types. To learn more about tab-delimited text files, read Tab-Delimited File Tips.
  • The formatting is unsupported.
    Exported files from other ESPs may not be formatted in a way that our import tool can manage, so you may have to do some reformatting to make it work. To learn more, read Format Guidelines for your Import File.
  • There are too many groups.
    We can only support 60 groups per audience. If you switch from Constant Contact with 60 groups or more, you may see an error on your import.
    You can import OPTIN_TIME and CONFIRM_TIME fields, but they are only checked the first time you import a contact and can't be overwritten later. Also, future dates in these fields will cause an error, so double check that this field data is correct.
  • The file size is too large.
    If your CSV or TXT file size exceeds 200MB, or about one million contacts, it may cause import errors. If you experience an error when importing a large file, split up your file into several smaller files and import them individually.

My addresses have syntax errors.

Malformed or incomplete email addresses are treated as syntax errors and won't be added to your audience.

Here are some common causes of syntax errors.

  • A contact’s email address is missing information.
    An address could be missing something. For example, john@aol is missing ".com," and john@aolcom is missing the dot. Add the missing information and try again.
  • A contact’s email address has extra spaces.
    Because of how some export utilities work, an address may include unnecessary spaces before, after, or even in the middle of the address. These extra spaces can cause an otherwise valid address to be reported as a syntax error. Try the TRIM function in Excel to remove spaces from text, or search for a similar feature in your preferred spreadsheet application’s help documentation.
  • A contact’s email address contains typos.
    Mailchimp scans for misspellings of common domains and removes them from your import to prevent bounces. For example, we'll block "" or "" because Gmail and Yahoo were misspelled. Fix the typos and try again.
  • A contact’s email address has unsupported characters.
    To accommodate international languages, Mailchimp supports Unicode (UTF-8), ASCII, and extended ASCII characters. However, Mailchimp can’t process addresses with UTF-8 encoded characters in the email prefix, which is the text before the @ symbol. Check your contacts' email addresses for special or international characters in the email prefix. To learn more, read International Characters in Mailchimp.
  • Your file includes semicolons instead of commas.
    Some European spreadsheet programs use semicolons rather than commas to separate data fields in CSV or TXT files. This can cause problems with Mailchimp imports. If your import file uses semicolons as separators, replace them with commas and try your import again. To do this, upload your file to Google Drive and save it as a CSV or open the file in a text editor and use find and replace to update the punctuation.

My contact count doesn't match.

If the total number of imported contacts on your Import History page doesn’t match what you expected to see, there are a couple things to look for.

  • The import file includes role-based addresses.
    Email addresses defined by a job or title, like, are known as role-based addresses. Typically, these addresses are managed by several people and sometimes fall into disuse. This can lead to high bounce rates and spam complaints, so Mailchimp will automatically remove them from your import. You can still add contacts with role-based addresses to your audience, but you'll need to manually add them or request they subscribe via your audience's signup form.
  • There are more than 100,000 contacts.
    Audiences of more than 100,000 contacts can take some time to import. After the import is complete, we'll send a confirmation email to the primary account contact and post a notification in your Account drop-down menu.
  • You’ve enabled the Auto-Update feature.
    Auto-Update adds imported addresses as new subscribers and updates existing subscribers' profiles with new information. If an email address appears multiple times in your import file, we'll import it once as a new subscriber and update that profile with any new information in the subsequent rows. For example, if you import 10 addresses and one is a duplicate, your total subscriber count will only go up by 9. If Auto-Update is turned on, your import results will say "9 email addresses were updated or added."

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