SendKit
Cold-email infrastructure with a dedicated IP per account — campaigns, sequences, leads, DNC, and a deliverability surface (mailbox health, warmup, inbox-placement and blacklist tests). BYOK; free on Hyreflow.
Use SendKit for outbound email campaign management: create and sequence campaigns, push leads, start and pause sending, and pull analytics. SendKit's differentiator is dedicated-IP deliverability — it's the sequencer whose mailbox health, warmup progress and inbox-placement/blacklist tests you can read through the API, so a play can confirm a mailbox is ready before it sends instead of finding out from the bounce rate.
Free on Hyreflow (0 credits) — runs on your own connected SendKit account.
Capabilities
| Tool | Does | Cost |
|---|---|---|
list_campaigns | List campaigns (resolve a stable campaign ID) | Free |
create_campaign | Create a campaign — draft, nothing sends yet | Free |
update_campaign | Update a campaign's sequence/schedule/settings | Free |
add_campaign_leads | Add leads to a campaign (up to 5,000 per call) | Free |
start_campaign | Start sending — requires a mailbox, a sequence step, a lead | Free |
pause_campaign / resume_campaign | Pause or resume sending | Free |
get_campaign_analytics | Sent / opened / clicked / replied / bounced | Free |
list_leads / create_lead / create_leads_bulk | Manage the workspace-wide lead pool | Free |
list_dnc / add_dnc_entries | Read and add do-not-contact entries | Free |
list_mailboxes / get_mailbox_health | Mailbox status, bounce rate, health score | Free |
list_warmup_stats / get_warmup_config | Warmup progress and configuration per mailbox | Free |
create_inbox_placement_test | Send a seed test to check inbox placement | Free |
create_blacklist_test | Check a mailbox against blacklists | Free |
Guidance
- Auth is a workspace key (
sk_...), created in the SendKit UI under its API settings. A platform key (sk_user_...) needs a workspace header this integration doesn't send, so connecting one is rejected up front rather than passing a check and failing on every real call later. - Check deliverability before you send. Read
get_mailbox_healthand the warmup endpoints for a mailbox before assigning it to a campaign, not only once at connection time. - Gate activation behind enrichment/verification — only push leads that have been validated.
start_campaignandresume_campaigntrigger real outbound; confirm the mailbox, sequence and lead list first. - Resolve campaign IDs from
list_campaignsbefore any write. - Add or bulk-create leads in batches of up to 5,000 per call.
- Writes are at-least-once. A rate-limited or 5xx response is retried automatically, so a write
whose reply was lost after it landed can apply twice. Enrolling leads is safe — SendKit skips
ones already in the campaign, and bulk lead creation skips duplicates by email.
create_campaignand the two deliverability tests are not: read back before re-issuing one yourself.
hyreflow tools execute sendkit add_campaign_leads \
--payload '{"campaign_id":"campaign_123","leads":[{"email":"[email protected]","firstName":"Ada","companyName":"Acme"}]}'Building a campaign is free; sending is the irreversible step. Keep start_campaign behind an
explicit approval gate — see Campaign Plays.