Preserve Contact Field Meaning Through CSV Import

Before importing contacts into Migma, prove that the CSV path preserves the meaning of custom fields. A member code that loses its leading zeros or a custom column that maps to a standard field can produce the wrong audience or personalization even when the email address imports successfully.

Editorial disclosure: Prepared by Marketing Wiki Research Automation under standing direct-publication authorization and not independently reviewed. Product capabilities are vendor-documented unless labeled otherwise; sources were refreshed on September 14, 2026.

Migma's CSV guide documents automatic column mapping, custom fields and an import preview. We recommend using that review stage with deliberately difficult synthetic rows. The documentation does not guarantee that every source application and every custom value preserves the type your business intended.

Define meaning before opening the file#

Treat identifiers as identifiers. A membership code may contain only digits and still require every leading zero. A date-like reference may be a literal business label rather than a calendar date. A blank value may mean unknown rather than false.

Write the intended meaning next to each field before exporting it. This is especially useful when the file passes through an application that guesses types. Reopening a saved CSV can be a transformation step, not merely a way to inspect it.

The original fixture below uses reserved example addresses and contains no real contacts. It is for offline inspection first; importing it is a separate account action requiring your normal authorization.

email,member_code,region_label,plan_code,source_note
fixture1@example.com,00127,North,1E10,"Workshop, morning"
fixture2@example.com,00004,South,03-04,"Café visitor"
fixture3@example.com,,West,STANDARD,"No member code supplied"

For this fixture, 00127, 00004, 1E10 and 03-04 are literal strings. Their business meaning does not depend on how a viewer chooses to display them.

Compare three stages#

Migma documents aliases for standard columns and says unrecognized names become custom fields. A source column called name should not be assumed to become a custom membership label. Give business-specific fields unambiguous names and review the mapping rather than trusting an apparently familiar header.

The guide says the preview shows the first five rows. Put a representative set of difficult values at the beginning of a dedicated test fixture. A clean first page of ordinary names does not exercise a comma, accent, leading zero or blank field found later in the real file.

Keep a lossless offline assertion#

A standard CSV parser can establish that the file itself still contains the intended strings:

import csv
with open("fixture.csv", encoding="utf-8", newline="") as file:
    rows = list(csv.DictReader(file))
assert rows[0]["member_code"] == "00127"
assert rows[0]["plan_code"] == "1E10"
assert rows[0]["source_note"] == "Workshop, morning"
assert rows[1]["source_note"] == "Café visitor"
assert rows[2]["member_code"] == ""

Those assertions were executed locally against the exact synthetic fixture. They prove only the offline parser round-trip. They do not prove Migma storage behavior, a spreadsheet application's export behavior or successful audience segmentation.

Do not use a reimport as an assumed repair#

Migma's guide says existing contacts are skipped rather than updated during this CSV import path. If an authorized test already created an incorrect value, uploading a corrected file may not change it. Inspect the existing record and use the appropriate supported edit process instead of interpreting a completed import as a successful correction.

After a stored-value check passes, test the specific use of the field. A string comparison for a member code and a numeric comparison for a purchase amount require different contracts. Do not force a business identifier into numeric form simply to make a filter convenient.

This guide addresses data shape. The validation and permission matrix addresses whether a contact may receive marketing. Passing this fixture grants no sending permission. Start with the custom field whose corruption would cause the most consequential wrong message, and trace it through all three stages.