A little extra care with your file, and a clear plan for how you'll keep adding recipients over time, makes CSV Upload automations far easier to manage — especially once you're running one on an ongoing basis instead of as a single one-time send.
Formatting your file for a clean import
Pick one address format and use it consistently. Either provide a single FullAddress column, or split it into Address1 / City / State / ZipCode — don't mix both approaches within the same file.
Keep zip codes as plain, 5-digit US zip codes. Extra characters or ZIP+4 formatting can cause an address to fail validation.
Give every row a name. At least one of FirstName, LastName, or ToOrganization is required for Mail to Recipients — a row with none of these will show up as an error on the review screen and won't be included until you fix it.
Only fill in Address2 when you have real unit information. LettrLabs' address-verification step fills in a validated Address2 automatically in most cases, so leaving it blank when you're unsure is usually safer than guessing.
Use the Custom columns intentionally. Custom1–Custom6 only add value if your template actually references them as mail-merge fields — decide what each column means before you build your list, and keep that mapping consistent across every file you upload to the same automation.
Watch the review screen, not just the "row_success" count. A file can "import" successfully and still contain rows with missing address or name fields, non-US addresses, or invalid characters — the review screen after upload (Step 4 of the Setup Guide) is where those actually surface.
Setting up recurring sends
CSV Upload doesn't poll an external system for new recipients on a schedule — every batch starts with someone in your organization uploading a file. That said, the same automation can absolutely support an ongoing, recurring cadence of new recipients:
Keep the automation Active and re-use it. The Add Recipients via CSV action is available on an active automation at any time — there's no need to create a new automation each time you have a new batch of leads or customers to mail. Upload weekly, monthly, or whatever cadence matches how your recipient lists are generated, and each new batch goes through the same review-and-approve step before it joins the mailing.
Don't confuse "Cadence" with "recurring uploads." The Cadence you configure in Step 1 (multi-touch templates with a delay between them) governs repeat mailings to the same batch of recipients you already uploaded — a follow-up postcard 14 days after the first, for example. It has nothing to do with bringing in a new batch of recipients; that's always a fresh CSV upload.
Re-uploading the same list won't double-mail people. Recipients are automatically checked against duplicates already in the automation, against your suppression audience, and against your do-not-mail list, and flagged accordingly on the review screen — so accidentally including someone from a prior upload in your next file is a low-risk mistake, not a costly one.
Recently-mailed recipients get a warning, not a silent re-send. If a new batch includes people who were mailed very recently, you'll see a warning before you confirm the upload, giving you a chance to reconsider before spending on a mailer they likely don't need yet.
Set your monthly sending limit with recurring volume in mind. The limit you set in Step 1 applies to the automation as a whole, across every touch in its cadence — if you're planning to top it up with new recipients every week or month, size the limit for your expected ongoing volume rather than just your first upload.
Example: a home services company exports its "new customer" report from its billing system every Monday morning and uploads it to the same CSV Upload automation. Each week's batch goes through the same review-and-approve step, then joins the existing cadence — so the automation behaves like an always-on welcome mailer without ever needing to be recreated.