REST for application control
REST is the straightforward choice for provisioning inboxes, listing threads, sending replies, managing labels, and configuring webhooks from your backend. It exposes stable resources and works well with typed SDKs.
MCP for model-facing tools
MCP lets a compatible agent client discover email tools and invoke them with structured inputs. It reduces one-off tool wrappers, while authorization and workspace scope remain enforced by AgentMailer.
A2A for agent delegation
A2A describes an agent and supports structured messages and tasks. It complements email: use email when the counterparty is a person or existing service, and A2A when another agent can accept a structured task directly.
IMAP and SMTP for compatibility
IMAP gives existing clients and libraries access to mailbox state. SMTP lets legacy software submit messages. They are essential compatibility surfaces, but a new agent integration usually benefits from the richer identity, threading, event, and authorization model in REST or MCP.
Frequently asked questions
Does MCP replace IMAP?
No. MCP exposes model-friendly tools; IMAP exposes standard mailbox access. They serve different clients.
Does A2A replace email?
No. A2A improves structured agent communication, while email remains the broadly compatible channel for people and existing services.