As a survey gains more and more responses, the size of an export can increase significantly leading to a number of issues such as slowing down the export itself, using up file library quotas and increasing the time to download them. If you are storing them yourselves, it can also take up a significant amount of space.
Also, if an export is larger than 50MB, it will not be attached to the export email if that feature is being used.
A CSV "All responses" export for a large survey could be greater than 600MB. As Excel, it would be 400MB (although this option is not available on very large surveys) but zipped, would only be around 40MB.
SmartSurvey has introduced a new feature that will be enabled by default that will automatically zip all exports that are larger than 50MB in size. This will mean that many more exports that are currently too large to email will be emailed again but it will also mean that you will need software to unzip these files if you need to read them. Microsoft Windows contains built-in functionality to unzip files but you will need to check your MacOS or Linux machines to ensure you have a suitable utility.
Once zipped, the export will be attached, stored and downloaded in the zip file format.
There is also an option in the export page to zip a file regardless of size and always zip scheduled exports, which means the format won't change if it grows larger than 50MB. This can be useful if you have setup automation and can always know it will arrive in the email or be pulled from the API in the same format.