The text file must meet with the following requirements:
1. Column header is required and should be included as the very first line, and should specify the following header names (case insensitive)
1. first: column for person first name, REQUIRED
2. last: column for person last name, REQUIRED
3. company: person's company name
4. email: person's email 5. uniqueId: person's unique id
6. mobileNumber: person's mobile phone number
7. custom1
8. custom2
9. custom3
10. custom4
11. custom5
First and last header names are mandatory, and others are optional.
For example, this import file contains three columns for first name, last name, and company.
3. The Import file is considered invalid if column header line does not contain "first" and "last", or if it contains any other unrecognized header names.