Migration guides: beehiiv, Substack and Mailchimp to SendLit #68

Background

There is no migration documentation for newsletter senders:

• The getting-started docs are two short pages: apps/docs/content/docs/getting-started/overview.mdx (17 lines) and first-broadcast.mdx (15 lines).
• first-broadcast.mdx:8 says "Create or import contacts", but there is no import yet (CSV contact import and export #38).
• There's no guide for moving from beehiiv, Substack or Mailchimp.

beehiiv raised prices about 42% (Oct 2026), and creators such as Nevo David are actively looking to move. MailCheap is already pitching beehiiv/Substack/Mailchimp import.

beehiiv export facts (beehiiv help articles 12258595483543 and 12428610562327):

• Two export variants. Quick/Basic has email, status, tier. Full adds custom fields and stats.
• Statuses are Active / Paused / Pending / Needs Approval / Inactive.
• Exports are found at Settings → Export Data, and download links expire after 24h.

Needed soon after we start inviting beehiiv switchers. Depends on #38.

Proposed fix

Write a docs section "Migrate to SendLit" with one page each for beehiiv, Substack and Mailchimp. Each page covers:

1. exporting subscribers from the old tool (and posts, for later archive import)
2. connecting your sending provider (link to the SES guide Write a 'SendLit with Amazon SES in ~15 minutes' guide #28 and the warm-up guide)
3. domain authentication (SPF/DKIM/DMARC, Built-in DKIM/SPF/DMARC guidance #4)
4. importing the CSV, with the status mapping from CSV contact import and export #38
5. recreating signup forms (Public subscribe endpoint and embeddable signup form #27), welcome sequences and tags
6. sending a test, then your first scheduled broadcast
7. a pre-switch checklist (mailing address, unsubscribe, reply-to)

Acceptance criteria

• "Migrate to SendLit" section on docs.sendlit.app, with beehiiv, Substack and Mailchimp pages
• Each page documents the source tool's export steps and its status → SendLit mapping
• Linked from getting-started and from the import UI once CSV contact import and export #38 ships
• first-broadcast.mdx no longer promises import before it exists (or links to the guide)