# Use the web inbox > Read, search, organize, compose, and reply from Startup Mail’s focused mail surface. ## Use the combined inbox Choose **Combined inbox** in the mailbox selector to triage all mailboxes you can access on one screen. Every conversation shows the original delivered-to address, so messages sent to `support@product-a.com` remain distinguishable from messages sent to `billing@product-c.com`. Opening a conversation keeps its owning mailbox intact, and replies send from that mailbox’s address. ## Switch mailboxes Use the mailbox selector in the left navigation to move between individual addresses you can access. Shared and private mailboxes are marked separately. Unread counts belong to each mailbox. ## Work with conversations Messages are grouped into threads. Opening a thread marks it read and shows the complete conversation in chronological order. The inbox supports Inbox, Starred, and Sent views; archive and trash actions remove a thread from the active inbox without changing another user’s mailbox permissions. Search looks across the accessible conversation list. Compose suggests people you contacted recently without requiring a separate contacts database. ## Compose and reply Choose **Compose**, select an available sending mailbox, enter up to ten recipients in each recipient field, add a subject, and write plain or formatted content. Replies keep the existing thread relationship. Attachments are uploaded before the message is queued. A single attachment can be up to 5 MB, a message can contain up to ten attachments, and the entire message must stay under the configured 10 MB boundary. ## Delivery status An outgoing message first appears as queued. Provider feedback can move it to sent, delivered, or failed. A failed status is about that message delivery; repeated hard bounces or complaints can also suppress a recipient or pause workspace sending. > **HTML is treated as untrusted** > > Incoming HTML is cleaned and shown in a restricted frame. Remote resources are blocked so merely > opening a message does not silently load tracking content.