Start with the country code
Use a plus sign, the country code, and the full phone number. For example, +12125550143 is a fictional US number in the format expected by a messaging integration. Keep phone columns as text in your spreadsheet so the plus sign and digits survive an export.
Miss Blue’s contact and conversation forms remove common spaces, brackets, dashes, and dots. A ten-digit North American number without a country code is interpreted with +1. For other countries, enter the full international form yourself; do not rely on that North American default.
Check a suggested correction before accepting it
A number beginning with + already states a country code. Miss Blue may suggest a correction when it looks like +1 was omitted, but the suggestion is not proof of the recipient’s country. Confirm it against your original contact record.
Remove extensions and descriptive text from the recipient field. Formatting checks can detect an invalid shape; they cannot establish that the number belongs to the intended person or supports iMessage.
Use an email only when it is an iMessage destination
An Apple ID email can be a messaging handle. It does not become a phone number, and it cannot receive an ordinary phone call. Confirm which address the recipient uses for iMessage.
The same person’s phone number and email can have separate conversations and separate new-lead analytics entries. Renaming a contact does not merge those identities.