When a Marketing Campaign is integrated with Mailchimp you can provide a "Public Name". This is the name that the recipient will see when you send the email campaign and it can be different from the actual name of the campaign if required.

There is a limitation to the number of characters that can be passed across to Mailchimp in regards to the "Public Name" which is 100 characters. Unfortunately this is a limitation of the Mailchimp API at the time of writing.

If one of your Marketing Campaigns has a value in this field over 100 characters, the integration will fail with an error message similar to the below in the Process Logs:

The integration works based on unique ID's and processes campaigns in ascending ID order. Thus, if your Marketing Campaign happens to be in the middle of the list to process, any Campaign with an ID higher than the problematic one will also fail.

To correct this problem, you'll need to identify the Marketing Campaign and shorten its public name. Click Start > Configuration > Automation > Processes > Scheduled Processes. Open the Scheduled Process called "_sync to the Mailchimp List" and then click the Logs tab.

You should see at least one failure line with the exit code of "1(Retry Later)" and the error message given above. Open one of these rows, and page to the very end of the logging to find a debugging line:

Open this up, to reveal the error message and the campaign name:

You can then search for this Campaign and rename it with a shorter name. Once you are happy, save the record and then revisit the process again. The process has more than likely disabled itself when the failure happened so you will need to tick the "Enabled" checkbox again on the main tab.