Does Zernio support iMessage availability check?

Zernio does not list iMessage availability check on its site or in its docs.

Does Zernio support line pooling?

Zernio does not list line pooling on its site or in its docs.

Inkbox vs Zernio

Q: How much do Inkbox and Zernio cost?

Inkbox: Free covers 3 identities with shared iMessage; Developer is $25 a month with a VoIP number; Startup is $167 a month with one dedicated iMessage number; Enterprise is custom. SMS/MMS and call minutes over allowance cost $0.03 each. Zernio: An iMessage sender costs $200 a month plus Zernio's per-account fee, with a free sandbox; SMS, calls and outbound messages past 10,000 a month are metered.

Compare Inkbox and Zernio side by side: iMessage features, channels, developer tools, pricing and compliance, checked on each provider's own site.

Inkbox

Email, phone, iMessage and A2A identity for AI agents

Starting price: $25/month (Developer); $167/month for a dedicated iMessage number (Startup)
Free plan: Free: 3 identities, shared iMessage up to 2,000 messages a month and 3 recipients at a time

Visit Inkbox Read more

Zernio

One API for iMessage, SMS, WhatsApp, social DMs and calls

Starting price: $200/month per iMessage sender
Free plan: First 2 connected accounts free; free iMessage sandbox on a shared line

Visit Zernio Read more

Inkbox supports 45 of the 77 features compared here, and Zernio supports 57.

Where Inkbox is ahead

Where Zernio is ahead

and 8 more in the table below.

Feature comparison

Feature	Inkbox	Zernio
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.	SupportedGroups on ordered senders: reply, create, rename, photo, members. Not on the sandbox line.
Group management	PartialCreate a group by sending to 2 to 8 numbers. No add or remove member API in V1.	SupportedStart a group from a sender and add or remove participants; applied asynchronously.
Group name and photo	Not listed	SupportedRename a group or change its photo, one change per call.
Mentions	Not listed	Not listed
Tapbacks	SupportedSend, replace and remove 7 tapbacks including eyes; inbound tapbacks arrive by webhook.	SupportedSix Apple tapbacks plus custom emoji (iOS 18+). Inbound reactions arrive by webhook.
Threaded replies	Supportedreply_to_message_id in 1:1 and group chats, with thread reads. Falls back to a plain reply.	SupportedreplyTo on sends; inbound messages carry the reply thread id.
Typing indicators	PartialSend only, in 1:1 chats. Groups and inbound typing events are not supported.	PartialSend only, 1:1 chats, about 15 seconds, after a recent two-way exchange.
Read receipts	PartialSend read receipts in 1:1 chats. No read status for your own sent messages is documented.	PartialMark a chat read inside an active two-way chat. Webhook docs list message.read for other platforms only.
Edit and unsend	Not listed	SupportedEdit text within 15 minutes; unsend within 2 minutes removes the bubble for the recipient.
Message effects	Supported4 bubble and 9 full-screen send styles, in 1:1 and dedicated-line groups.	Supported13 screen and bubble effects, such as slam, invisibleInk, confetti and fireworks.
Animated text effects	Not listed	Not listed
Stickers	Not listed	PartialInbound stickers are typed as sticker. Sending stickers is not documented.
Formatted text	Not listed	SupportedInline bold, _italic_, __underline__ and ~strikethrough~ markup renders as rich text.
Attachments	SupportedOne media item per message, uploads up to 10 MiB. No media before the recipient's first reply.	SupportedUp to 10 per message, each a public https URL of at most 256 characters.
Live Photos	Not listed	Not listed
Rich link previews	Not listed	SupportedOn by default; linkPreview: false sends links as plain text.
Voice messages	Not listed	SupportedvoiceNote: true on an audio file. Inbound voice messages come with a transcript.
Contact cards	PartialThe router sends the agent's contact card on connect. Sending other vCards is not documented.	PartialcontactCard shares the sender's own card only.
Polls	Not listed	Not listed
Chat backgrounds	Not listed	Not listed
Location sharing	Not listed	PartialStatic location pins only. Inbound shared locations arrive without coordinates.
iMessage apps	Not listed	Not listed
Live app cards	Not listed	Not listed
Sender name and photo	SupportedDedicated lines share the identity's display name and avatar automatically.	PartialSets the name and photo on the sender's contact card, which recipients see when they save it.
FaceTime calls	Not listedCalls run over iMessage lines, but the docs do not say whether they are FaceTime.	Not listedInbound FaceTime attempts show in the thread as call-typed messages. No calling documented.
Delivery status	Supportedimessage.sent, imessage.delivered and imessage.delivery_failed webhooks, per recipient in groups.	Supportedmessage.delivered and message.failed webhooks; sends deferred for pacing show as queued.
iMessage availability check	SupportedReturns iMessage, SMS or RCS for any E.164 number.	Not listed
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.	SupportedZernio orders numbers on its delivery provider's Apple-registered infrastructure.
Dedicated numbers	SupportedStartup plan includes one dedicated iMessage number. VoIP numbers for calls and SMS from Developer.	SupportedUS or UK numbers, some active instantly; email-handle senders through the API.
Shared numbers	SupportedFree and paid plans include shared iMessage. The human must text the router first.	SupportedFree shared sandbox line for testing: contact writes first, 5 contacts, 50 messages a day.
Bring your own number	Not listed	PartialiMessage cannot run on a number you own. A sender held with the provider can be registered.
Line pooling	BetaOrganization-owned shared iMessage pools, beta and by request only.	Not listedOne sender per profile; docs suggest spreading contacts across senders by hand.
SMS fallback	SupportedInkbox tries iMessage first and can fall back to SMS; was_downgraded marks it.	SupportedSMS or RCS from the same number when the contact is not on iMessage.
RCS fallback	PartialDocs describe SMS fallback, and the service field can report rcs. The transport cannot be chosen.	SupportedSMS or RCS from the same number; the provider picks per contact.
Outbound-first messaging	PartialDedicated lines can start chats, up to 40 new recipients a day. Shared service needs the human to text first.	SupportedOne new chat per 15 minutes per sender, warm-up from 2 to 50 a day, no links in openers.
Calls on the iMessage number	SupportedAgents place and receive voice calls over shared and dedicated iMessage lines.	PartialOrdered numbers include call forwarding. Placing calls from the iMessage number is not documented.
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.	Supported
WhatsApp	Not supportedNot offered	Supported
Telegram	Not supported	Supported
Slack	BetaSlack is in beta: read, reply, files and retained history search.	Supported
Email	SupportedEach identity gets a mailbox, with custom domains and IMAP/SMTP access.	Not supportedNot offered as a channel. iMessage senders can use an email handle.
Phone calls	SupportedInbound and outbound calls with your own WebSocket agent or Inkbox Voice AI (beta).	SupportedInbound and outbound PSTN calls, SIP trunks, browser softphone, recording and transcription.
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.	SupportedSame inbox send call and webhooks for iMessage, SMS, WhatsApp, Telegram, Slack and social DMs.
Developer tools
REST API	Supported	Supported
TypeScript SDK	Supported@inkbox/sdk	Supported@zernio/node
Python SDK	Supportedinkbox on PyPI	Supportedzernio-sdk
Other SDKs	SupportedRust SDK (inkbox crate).	SupportedGo, Ruby, Java, PHP, .NET and Rust.
CLI	Supported@inkbox/cli	SupportedZernio CLI, including iMessage inbox sends and reactions.
Webhooks	Supported	Supported
Signed webhooks	SupportedHMAC-SHA256 with a per-identity signing key.	SupportedHMAC-SHA256 of the raw body in X-Zernio-Signature, keyed by your secret.
MCP server	SupportedRemote Streamable HTTP endpoint at inkbox.ai/mcp, with a separate ChatGPT endpoint.	SupportedHosted at mcp.zernio.com/mcp, with OAuth sign-in or an API key.
Open source	PartialSDK, CLI, skills and examples are MIT on GitHub. The service is closed.	PartialSDKs, CLI, n8n node and Chat SDK adapter are MIT or Apache-2.0. The platform is closed.
Self-hosting	Not listed	Not supportedHosted cloud service only
Local testing	Not listed	Not listedThe free sandbox still needs your own phone or Apple ID.
Custom channel providers	Not listed	Not listed
Event replay	SupportedDelivery log with replay. Incoming-call and Slack deliveries cannot be replayed.	Supported7 attempts over about 51 hours, then dead-letter; any past event can be redelivered.
OpenTelemetry	Not listed	Not listed
No-code integrations	Not listed	Partialn8n, Make and Zapier guides cover posting; Make's API call module reaches any endpoint.
CRM integrations	Not listed	SupportedHubSpot: inbox contacts and messages sync to HubSpot timelines.
Built for AI agents
Agent framework	PartialIdentity layer with contact memories across email, texts and calls. No conversation framework.	PartialWorkflow engine with AI and handoff nodes; the workflow docs do not list iMessage.
Agent framework integrations	SupportedPlugins for Hermes Agent, OpenClaw, OpenCode, Codex, Claude Code and DeepSeek Harness.	PartialVercel Chat SDK adapter (iMessage not listed) and an OpenClaw skill.
Streaming replies	Not listed	PartialChat SDK adapter streams by editing on Telegram only.
Agent group chats	Not listedAgents can reach each other over A2A tasks, but not in group chats.	Not listed
Human handoff	PartialPeople can reply from the Console, and Voice AI can transfer a call. No handoff controls for agents.	PartialDashboard inbox and workflow handoff nodes; no iMessage-specific handoff documented.
Audit logs	Not listed	SupportedAppend-only log of team-management actions; Enterprise adds broader audit logs.
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.	SupportedFirst 2 connected accounts free; free iMessage sandbox (5 contacts, 50 messages a day).
Public pricing	Supported	Supported$200 per iMessage sender per month, plus the connected-account fee.
No per-message fees	PartialiMessage is capped per plan with no per-message fee. Extra SMS/MMS and call minutes cost $0.03 each.	PartialiMessage pages say no per-message fee; an outbound meter of $1 per 10,000 after 10,000 starts Oct 2026.
Uptime SLA	Not listed	Not listedSite states 99.97% uptime; no contractual SLA found.
Isolated infrastructure	PartialDedicated iMessage infrastructure is listed for Enterprise only.	Not listed
SOC 2 Type II	Not listed	SupportedSOC 2 Type II report in the trust portal, by access request.
GDPR	Not listedThe DPA names the CCPA only; GDPR is not mentioned.	SupportedGDPR documentation in the trust portal; public DPA.

Feature

Inkbox

Zernio

iMessage messaging

iMessage

Shared router service on every plan, or a dedicated line from the Startup plan.

Group chats

Dedicated lines only, 2 to 8 remote participants. Shared service is 1:1.

Groups on ordered senders: reply, create, rename, photo, members. Not on the sandbox line.

Group management

PartialCreate a group by sending to 2 to 8 numbers. No add or remove member API in V1.

Start a group from a sender and add or remove participants; applied asynchronously.

Group name and photo

Not listed

Rename a group or change its photo, one change per call.

Mentions

Not listed

Tapbacks

Send, replace and remove 7 tapbacks including eyes; inbound tapbacks arrive by webhook.

Six Apple tapbacks plus custom emoji (iOS 18+). Inbound reactions arrive by webhook.

Threaded replies

reply_to_message_id in 1:1 and group chats, with thread reads. Falls back to a plain reply.

replyTo on sends; inbound messages carry the reply thread id.

Typing indicators

PartialSend only, in 1:1 chats. Groups and inbound typing events are not supported.

PartialSend only, 1:1 chats, about 15 seconds, after a recent two-way exchange.

Read receipts

PartialSend read receipts in 1:1 chats. No read status for your own sent messages is documented.

PartialMark a chat read inside an active two-way chat. Webhook docs list message.read for other platforms only.

Edit and unsend

Not listed

Edit text within 15 minutes; unsend within 2 minutes removes the bubble for the recipient.

Message effects

4 bubble and 9 full-screen send styles, in 1:1 and dedicated-line groups.

13 screen and bubble effects, such as slam, invisibleInk, confetti and fireworks.

Animated text effects

Not listed

Stickers

Not listed

PartialInbound stickers are typed as sticker. Sending stickers is not documented.

Formatted text

Not listed

Inline *bold*, _italic_, __underline__ and ~strikethrough~ markup renders as rich text.

Attachments

One media item per message, uploads up to 10 MiB. No media before the recipient's first reply.

Up to 10 per message, each a public https URL of at most 256 characters.

Live Photos

Not listed

Rich link previews

Not listed

On by default; linkPreview: false sends links as plain text.

Voice messages

Not listed

voiceNote: true on an audio file. Inbound voice messages come with a transcript.

Contact cards

PartialThe router sends the agent's contact card on connect. Sending other vCards is not documented.

PartialcontactCard shares the sender's own card only.

Polls

Not listed

Chat backgrounds

Not listed

Location sharing

Not listed

PartialStatic location pins only. Inbound shared locations arrive without coordinates.

iMessage apps

Not listed

Live app cards

Not listed

Sender name and photo

Dedicated lines share the identity's display name and avatar automatically.

PartialSets the name and photo on the sender's contact card, which recipients see when they save it.

FaceTime calls

Not listedCalls run over iMessage lines, but the docs do not say whether they are FaceTime.

Not listedInbound FaceTime attempts show in the thread as call-typed messages. No calling documented.

Delivery status

imessage.sent, imessage.delivered and imessage.delivery_failed webhooks, per recipient in groups.

message.delivered and message.failed webhooks; sends deferred for pacing show as queued.

iMessage availability check

Returns iMessage, SMS or RCS for any E.164 number.

Not listed

Focus and Notify Anyway

Not listed

Numbers and delivery

Managed lines

Shared router lines and dedicated lines run by Inkbox. No Mac needed.

Zernio orders numbers on its delivery provider's Apple-registered infrastructure.

Dedicated numbers

Startup plan includes one dedicated iMessage number. VoIP numbers for calls and SMS from Developer.

US or UK numbers, some active instantly; email-handle senders through the API.

Shared numbers

Free and paid plans include shared iMessage. The human must text the router first.

Free shared sandbox line for testing: contact writes first, 5 contacts, 50 messages a day.

Bring your own number

Not listed

PartialiMessage cannot run on a number you own. A sender held with the provider can be registered.

Line pooling

BetaOrganization-owned shared iMessage pools, beta and by request only.

Not listedOne sender per profile; docs suggest spreading contacts across senders by hand.

SMS fallback

Inkbox tries iMessage first and can fall back to SMS; was_downgraded marks it.

SMS or RCS from the same number when the contact is not on iMessage.

RCS fallback

PartialDocs describe SMS fallback, and the service field can report rcs. The transport cannot be chosen.

SMS or RCS from the same number; the provider picks per contact.

Outbound-first messaging

PartialDedicated lines can start chats, up to 40 new recipients a day. Shared service needs the human to text first.

One new chat per 15 minutes per sender, warm-up from 2 to 50 a day, no links in openers.

Calls on the iMessage number

Agents place and receive voice calls over shared and dedicated iMessage lines.

PartialOrdered numbers include call forwarding. Placing calls from the iMessage number is not documented.

Other channels

SMS

SMS and MMS on dedicated VoIP numbers, US and Canada included. Group MMS is beta.

RCS

PartialOnly as a transport reported on iMessage lines; not a channel you can pick.

Not supportedNot offered

Not supported

Slack

BetaSlack is in beta: read, reply, files and retained history search.

Each identity gets a mailbox, with custom domains and IMAP/SMTP access.

Not supportedNot offered as a channel. iMessage senders can use an email handle.

Phone calls

Inbound and outbound calls with your own WebSocket agent or Inkbox Voice AI (beta).

Inbound and outbound PSTN calls, SIP trunks, browser softphone, recording and transcription.

Apple Messages for Business

Not supportedNot offered

Unified channel API

PartialOne identity and one webhook subscription across channels, but separate APIs per channel.

Same inbox send call and webhooks for iMessage, SMS, WhatsApp, Telegram, Slack and social DMs.

Developer tools

REST API

TypeScript SDK

@inkbox/sdk

@zernio/node

Python SDK

inkbox on PyPI

zernio-sdk

Other SDKs

Rust SDK (inkbox crate).

Go, Ruby, Java, PHP, .NET and Rust.

CLI

@inkbox/cli

Zernio CLI, including iMessage inbox sends and reactions.

Webhooks

Signed webhooks

HMAC-SHA256 with a per-identity signing key.

HMAC-SHA256 of the raw body in X-Zernio-Signature, keyed by your secret.

MCP server

Remote Streamable HTTP endpoint at inkbox.ai/mcp, with a separate ChatGPT endpoint.

Hosted at mcp.zernio.com/mcp, with OAuth sign-in or an API key.

Open source

PartialSDK, CLI, skills and examples are MIT on GitHub. The service is closed.

PartialSDKs, CLI, n8n node and Chat SDK adapter are MIT or Apache-2.0. The platform is closed.

Self-hosting

Not listed

Not supportedHosted cloud service only

Local testing

Not listed

Not listedThe free sandbox still needs your own phone or Apple ID.

Custom channel providers

Not listed

Event replay

Delivery log with replay. Incoming-call and Slack deliveries cannot be replayed.

7 attempts over about 51 hours, then dead-letter; any past event can be redelivered.

OpenTelemetry

Not listed

No-code integrations

Not listed

Partialn8n, Make and Zapier guides cover posting; Make's API call module reaches any endpoint.

CRM integrations

Not listed

HubSpot: inbox contacts and messages sync to HubSpot timelines.

Built for AI agents

Agent framework

PartialIdentity layer with contact memories across email, texts and calls. No conversation framework.

PartialWorkflow engine with AI and handoff nodes; the workflow docs do not list iMessage.

Agent framework integrations

Plugins for Hermes Agent, OpenClaw, OpenCode, Codex, Claude Code and DeepSeek Harness.

PartialVercel Chat SDK adapter (iMessage not listed) and an OpenClaw skill.

Streaming replies

Not listed

PartialChat SDK adapter streams by editing on Telegram only.

Agent group chats

Not listedAgents can reach each other over A2A tasks, but not in group chats.

Not listed

Human handoff

PartialPeople can reply from the Console, and Voice AI can transfer a call. No handoff controls for agents.

PartialDashboard inbox and workflow handoff nodes; no iMessage-specific handoff documented.

Audit logs

Not listed

Append-only log of team-management actions; Enterprise adds broader audit logs.

Message history API

List and read conversations and threads, with search on texts and email.

Plans and compliance

Free plan

Free: 3 identities, shared iMessage up to 2,000 messages a month and 3 recipients at a time.

First 2 connected accounts free; free iMessage sandbox (5 contacts, 50 messages a day).

Public pricing

$200 per iMessage sender per month, plus the connected-account fee.

No per-message fees

PartialiMessage is capped per plan with no per-message fee. Extra SMS/MMS and call minutes cost $0.03 each.

PartialiMessage pages say no per-message fee; an outbound meter of $1 per 10,000 after 10,000 starts Oct 2026.

Uptime SLA

Not listed

Not listedSite states 99.97% uptime; no contractual SLA found.

Isolated infrastructure

PartialDedicated iMessage infrastructure is listed for Enterprise only.

Not listed

SOC 2 Type II

Not listed

SOC 2 Type II report in the trust portal, by access request.

GDPR

Not listedThe DPA names the CCPA only; GDPR is not mentioned.

GDPR documentation in the trust portal; public DPA.

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

Pricing

Inkbox

Free covers 3 identities with shared iMessage; Developer is $25 a month with a VoIP number; Startup is $167 a month with one dedicated iMessage number; Enterprise is custom. SMS/MMS and call minutes over allowance cost $0.03 each.

Pricing model: monthly plans with allowances, plus per-unit SMS/MMS and call-minute overage

Source

Zernio

An iMessage sender costs $200 a month plus Zernio's per-account fee, with a free sandbox; SMS, calls and outbound messages past 10,000 a month are metered.

Pricing model: flat per sender, plus per connected account and usage meters

Source