If you use our current ‘Traditional webmail’, you should export your contacts to a local file by using the defaults for "SquirrelMail" in the export contacts section.
If you wish to keep your whitelist and blacklists, you will need to copy them by hand to a local file.
NOTE: The old system sometimes used a tilde (~) to denote beginning and end of entries. Do not include this character in your list, it will prevent the new system from accepting that address during import.
