Inkbox vs Sendblue

Inkbox supports 45 of the 77 features compared here, and Sendblue supports 58.

Feature comparison

Feature	Inkbox	Sendblue
iMessage messaging
iMessage	SupportedShared router service on every plan, or a dedicated line from the Startup plan.	Supported
Group chats	SupportedDedicated lines only, 2 to 8 remote participants. Shared service is 1:1.	BetaGroup API is in beta on select plans. AI Agent plan can only reply in existing groups.
Group management	PartialCreate a group by sending to 2 to 8 numbers. No add or remove member API in V1.	BetaAdd and remove participants in iMessage groups via the beta groups API.
Group name and photo	Not listed	SupportedRename groups and set group photos on supported lines.
Mentions	Not listed	Not listed
Tapbacks	SupportedSend, replace and remove 7 tapbacks including eyes; inbound tapbacks arrive by webhook.	PartialSend classic tapbacks or any emoji. No inbound reaction events documented.
Threaded replies	Supportedreply_to_message_id in 1:1 and group chats, with thread reads. Falls back to a plain reply.	Supportedreply_to on V2 iMessage lines, in direct and group chats.
Typing indicators	PartialSend only, in 1:1 chats. Groups and inbound typing events are not supported.	SupportedSend and receive. iMessage 1:1 only, not in groups.
Read receipts	PartialSend read receipts in 1:1 chats. No read status for your own sent messages is documented.	PartialCan mark chats read (1:1). Outbound statuses stop at DELIVERED, with no read status.
Edit and unsend	Not listed	Not supportedDocs say editing is not supported via API and delete does not unsend.
Message effects	Supported4 bubble and 9 full-screen send styles, in 1:1 and dedicated-line groups.	Supported13 send_style values.
Animated text effects	Not listed	Not listed
Stickers	Not listed	Not listed
Formatted text	Not listed	Not listed
Attachments	SupportedOne media item per message, uploads up to 10 MiB. No media before the recipient's first reply.	SupportedUp to 100MB on iMessage, 5MB on SMS.
Live Photos	Not listed	Not listed
Rich link previews	Not listed	PartialDocs say links expand only after the recipient saves your contact.
Voice messages	Not listed	SupportedSend .caf files to render as inline voice notes.
Contact cards	PartialThe router sends the agent's contact card on connect. Sending other vCards is not documented.	SupportedSend .vcf files via media_url.
Polls	Not listed	Not listed
Chat backgrounds	Not listed	Not listed
Location sharing	Not listed	SupportedFind My request, read and live watch. Dedicated iMessage lines only.
iMessage apps	Not listed	SupportedApp Cards for your own Messages extension. V2 lines, not on the free plan.
Live app cards	Not listed	PartialUpdates go out as new messages in the same App Card session; Sendblue says the original is not edited.
Sender name and photo	SupportedDedicated lines share the identity's display name and avatar automatically.	SupportedName and Photo Sharing profile per line, shared into direct iMessage chats.
FaceTime calls	Not listedCalls run over iMessage lines, but the docs do not say whether they are FaceTime.	PartialOutbound FaceTime audio over WebRTC (Agora). Needs a purchased FaceTime line.
Delivery status	Supportedimessage.sent, imessage.delivered and imessage.delivery_failed webhooks, per recipient in groups.	SupportedStatus callbacks from REGISTERED through SENT or DELIVERED.
iMessage availability check	SupportedReturns iMessage, SMS or RCS for any E.164 number.	SupportedLookup API checks a phone number or email for iMessage.
Focus and Notify Anyway	Not listed	Not listed
Numbers and delivery
Managed lines	SupportedShared router lines and dedicated lines run by Inkbox. No Mac needed.	Supported
Dedicated numbers	SupportedStartup plan includes one dedicated iMessage number. VoIP numbers for calls and SMS from Developer.	Supported
Shared numbers	SupportedFree and paid plans include shared iMessage. The human must text the router first.	SupportedFree sandbox uses a shared number with verified contacts only.
Bring your own number	Not listed	PartialOnly by porting the number in, which adds 3 to 5 days.
Line pooling	BetaOrganization-owned shared iMessage pools, beta and by request only.	SupportedNumber pooling with sticky sending. Automatic line selection needs account enablement.
SMS fallback	SupportedInkbox tries iMessage first and can fall back to SMS; was_downgraded marks it.	Supported
RCS fallback	PartialDocs describe SMS fallback, and the service field can report rcs. The transport cannot be chosen.	SupportediMessage, then RCS, then SMS. RCS on V2 lines.
Outbound-first messaging	PartialDedicated lines can start chats, up to 40 new recipients a day. Shared service needs the human to text first.	SupportedFull outbound on Enterprise or Blue Ocean; Free and AI Agent plans are inbound-first
Calls on the iMessage number	SupportedAgents place and receive voice calls over shared and dedicated iMessage lines.	SupportedDashboard calls and FaceTime from the texting number; API calls via your Twilio caller ID.
Other channels
SMS	SupportedSMS and MMS on dedicated VoIP numbers, US and Canada included. Group MMS is beta.	Supported
RCS	PartialOnly as a transport reported on iMessage lines; not a channel you can pick.	SupportedV2 lines.
WhatsApp	Not supportedNot offered	Not supportedNot offered
Telegram	Not supported	Not supported
Slack	BetaSlack is in beta: read, reply, files and retained history search.	Not listed
Email	SupportedEach identity gets a mailbox, with custom domains and IMAP/SMTP access.	Not supportedNot offered. iMessage can be sent to Apple ID email addresses.
Phone calls	SupportedInbound and outbound calls with your own WebSocket agent or Inkbox Voice AI (beta).	PartialNo native calling API. Dashboard calls, outbound via your Twilio caller ID, inbound forwarding.
Apple Messages for Business	Not supportedNot offered	Not supportedNot offered
Unified channel API	PartialOne identity and one webhook subscription across channels, but separate APIs per channel.	SupportedOne API for iMessage, RCS and SMS, the only channels offered.
Developer tools
REST API	Supported	Supported
TypeScript SDK	Supported@inkbox/sdk	Supportedsendblue on npm.
Python SDK	Supportedinkbox on PyPI	Supportedsendblue on PyPI.
Other SDKs	SupportedRust SDK (inkbox crate).	PartialGo, Rust and Ruby packages, listed as community packages.
CLI	Supported@inkbox/cli	Supported@sendblue/cli: signup, messaging, contacts and webhooks.
Webhooks	Supported	Supported
Signed webhooks	SupportedHMAC-SHA256 with a per-identity signing key.	PartialSends your shared secret in an sb-signing-secret header. No HMAC signature.
MCP server	SupportedRemote Streamable HTTP endpoint at inkbox.ai/mcp, with a separate ChatGPT endpoint.	Supportedsendblue-api-mcp via npx.
Open source	PartialSDK, CLI, skills and examples are MIT on GitHub. The service is closed.	PartialSDKs and CLI are MIT or Apache-2.0 on GitHub. The messaging platform is closed.
Self-hosting	Not listed	Not listedSold as a hosted service on Sendblue's Apple devices; self-hosting is not mentioned.
Local testing	Not listed	Not listed
Custom channel providers	Not listed	Not listed
Event replay	SupportedDelivery log with replay. Incoming-call and Slack deliveries cannot be replayed.	PartialNo replay. Docs say to repair gaps by listing messages updated since a timestamp.
OpenTelemetry	Not listed	Not listed
No-code integrations	Not listed	SupportedZapier, Make and GoHighLevel. Docs FAQ says n8n resources are coming soon.
CRM integrations	Not listed	SupportedGoHighLevel, HubSpot, Salesforce, Close and Monday.com.
Built for AI agents
Agent framework	PartialIdentity layer with contact memories across email, texts and calls. No conversation framework.	PartialNo own framework. Maintains a Vercel Chat SDK adapter.
Agent framework integrations	SupportedPlugins for Hermes Agent, OpenClaw, OpenCode, Codex, Claude Code and DeepSeek Harness.	SupportedSendblue-maintained Vercel Chat SDK adapter.
Streaming replies	Not listed	Not supportedDocs say message editing is not supported via the API.
Agent group chats	Not listedAgents can reach each other over A2A tasks, but not in group chats.	BetaA line can add another of your own dedicated lines to a group, via the beta groups API.
Human handoff	PartialPeople can reply from the Console, and Voice AI can transfer a call. No handoff controls for agents.	SupportedShared team inboxes with assignment, and agents that escalate to a rep.
Audit logs	Not listed	PartialSecurity page says all API requests are logged. No customer-facing audit log documented.
Message history API	SupportedList and read conversations and threads, with search on texts and email.	Supported
Plans and compliance
Free plan	SupportedFree: 3 identities, shared iMessage up to 2,000 messages a month and 3 recipients at a time.	SupportedFree sandbox: shared number, up to 10 verified contacts, no webhooks.
Public pricing	Supported	SupportedAI Agent plan at $100/mo per line. Enterprise is custom.
No per-message fees	PartialiMessage is capped per plan with no per-message fee. Extra SMS/MMS and call minutes cost $0.03 each.	Supported
Uptime SLA	Not listed	Supported99.99% uptime SLA on the Enterprise plan
Isolated infrastructure	PartialDedicated iMessage infrastructure is listed for Enterprise only.	SupportedA dedicated HIPAA instance for HIPAA customers
SOC 2 Type II	Not listed	SupportedSOC 2 Type II, report on request.
GDPR	Not listedThe DPA names the CCPA only; GDPR is not mentioned.	SupportedPrivacy policy says Sendblue adheres to GDPR. DPAs on request.

Checked on each provider's own site and docs on 2026-10-25. “Not listed” means the provider does not mention it.

Pricing

Which should you choose?

Choose Inkbox if you need Slack and email.

Choose Sendblue if you need group name and photo, rich link previews, voice messages and location sharing.

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