> For the complete documentation index, see [llms.txt](https://help.openletterconnect.com/olc-help-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.openletterconnect.com/olc-help-docs/product-and-order-guide/sender-fields-and-sender-profiles/how-the-merge-works.md).

# How the Merge Works

* The Sender Profile dynamically merges Return Address data into the sender section of the mail piece
* This ensures consistent sender information across all campaigns using the same Sender Profile
* If you update a Sender Profile, changes will apply to future orders only

> **⚠️ Previously processed or already mailed orders will not be updated.**

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