Nylas connects to mailboxes your users own, and now hosts agent accounts too. MCPmailer gives agents their own address on your domain.
Agent inbox APIs · Nylas claims checked July 2026
Nylas is the long-standing answer to "let my product read and send from my users' Gmail and Outlook": one API across many providers, with calendar and contacts alongside mail. In 2026 it added Agent Accounts, Nylas-hosted mailboxes for agents, which brings it into this category from the other direction.
If your product needs to act inside a mailbox a human already owns, including their calendar and contacts, Nylas is the right tool and we are not a substitute. We do not connect to existing Gmail or Outlook accounts at all, by design.
When the agent needs an identity of its own rather than borrowed access to a person's, the connected-account model stops helping and starts charging: consent flows, token refresh, per-provider quirks, and a per-account fee on top of the mailbox licence you already pay. An address on your own subdomain with a scoped key has none of that.
Connected accounts assume a human is present to consent, at least once, and to re-consent when a token is revoked or a policy changes. A key scoped to one mailbox has no such moment. For a background agent that has to keep working at 3am on a Sunday, that is the difference between reliable and eventually broken.
Delegated access means a confused agent is loose in a person's mailbox, with their history and their contacts. Ours can only reach its own mailbox, and other identities in the workspace are invisible to it unless access was granted. When something goes wrong, the containment is structural rather than procedural.
The connected-account ladder charges per mailbox attached, and you still pay the provider for the underlying seat. We charge for a base plan plus the mail that actually moves, so ten agents that each send a hundred messages cost what a hundred messages cost, not what ten accounts cost.
Every row is a claim we could defend with their documentation open beside it. Where they are ahead, the row says so.
This is a design decision more than a vendor decision, and it usually splits cleanly.
Acting as a user
Stay with Nylas. If the agent must send from a named person's mailbox and see their calendar, nothing here replaces that.
Acting as itself
Come over. A support, sales, or scheduling agent that writes as the company wants its own address, not a borrowed one.
Both, which is common
Read a user's calendar through Nylas, then have the agent negotiate the meeting from its own address here.
No, and that is deliberate. Your agent gets its own address instead of access to a person's inbox, which keeps the blast radius of a mistaken agent to one mailbox. If you need to act inside a human's mailbox, use Nylas.
Same idea, different centre of gravity. Their published shape is a platform base fee that includes a number of agent accounts, then a small per-account price. Ours is a base plan plus metered mail, with MCP as the native interface and a supervision dashboard included.
No. If calendar access is essential, keep Nylas for that and let the agent converse from an address here.
Same answer as Gmail: we do not connect to them. See the Microsoft 365 comparison for why an agent usually wants its own address anyway.
If you are choosing between agent inbox APIs, the deciding question is usually where the conversation state lives. Ours lives in the mailbox, and your agent reaches it with tools instead of with a schema you maintain.
The free tier is 3,000 emails a month across three agent inboxes, no card, with receiving, threading, and search included. Enough to watch a real conversation happen before you decide.
More Agent inbox APIs