I have received recently a quite "weird" support case, in which the smart list is failing to export data into Excel addressing that Excel can not open the file. Here is the exact error message:
"Excel Cannot open file because the file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file"
|Smart list export error|
After several troubleshooting attempts suspecting that Excel is the source root cause, it rather appeared that "data" which is being exported is the root-cause of this error. It was found out that the data contains special characters. Here is the screen shot of the "corrupted" data record which was failing the whole process:
|An arrow Symbol (Special Character)|
Mahmoud M. AlSaadi