feat(mailbox): add capabilities page MTA-7016

pages/iam/reference-content/permission-sets.mdx

@@ -2,7 +2,7 @@
 title: Permission sets
 description: Explore how to define and manage permission sets for user access control.
 dates:
-  validation: 2025-11-13
+  validation: 2026-03-20
 ---
 
 Permissions sets and their scope make up [IAM rules](/iam/concepts/#rule), which define the access rights that a principal (user, group or application) should have. They consist of sets of one or multiple [permissions](/iam/concepts/#permission).
@@ -366,6 +366,13 @@ Below is a list of the permission sets available at Scaleway.
 | TransactionalEmailOfferSubscriptionFullAccess      | Full access to project offer subscriptions in transactional email    |
 | TransactionalEmailPoolReadOnly  | Read access to project pool in transactional email     |
 
+#### Mailbox
+
+|  Permission set   |      Description       |
+| :---------------: | :--------------------: |
+| MailboxFullAccess | Full access to Mailbox |
+|  MailboxReadOnly  | Read access to Mailbox |
+
 ### Monitoring
 
 #### Cockpit

pages/mailbox/menu.ts

@@ -33,7 +33,17 @@ export const mailboxMenu = {
       ],
       label: 'How to',
       slug: 'how-to',
-    }
+    },
+    {
+      items: [
+        {
+          label: 'Mailbox capabilities and limits',
+          slug: 'mailbox-capabilities-and-limits',
+        },
+      ],
+      label: 'Additional Content',
+      slug: 'reference-content',
+    },
   ],
   label: 'Mailbox',
   slug: 'mailbox',

pages/mailbox/reference-content/mailbox-capabilities-and-limits.mdx

@@ -0,0 +1,36 @@
+---
+title: Mailbox capabilities and limits
+description: Understand the capabilities and limits of Scaleway Mailbox.
+tags: mailbox-capabilities
+dates:
+  validation: 2026-03-20
+  posted: 2026-03-20
+---
+
+This page provides information about the capabilities and limits of Scaleway Mailbox.
+
+## Mailbox quotas
+
+- Mailbox storage: up to 20 GB per mailbox (for emails, attachments, and mailbox folders).
+- Number of Mailboxes: 20 Mailbox email accounts per project (during Beta phase). If you need to create more mailboxes, please contact the [Scaleway Support team](https://console.scaleway.com/support/tickets/create?for=product&productName=mailbox).
+
+## Message limits
+
+- `message` (the maximum number of messages that can be submitted per SMTP session): 10
+- `size` (the maximum size of a message): 104857600 bytes (100 MiB)
+- `received-headers` (the maximum number of received headers that a message can contain): 50
+
+## Supported ESMTP extensions
+
+Mailbox SMTP relay supports the following [ESMTP extensions](https://www.iana.org/assignments/mail-parameters/mail-parameters.txt):
+
+- 8BITMIME
+- BINARYMIME
+- CHUNKING
+- ENHANCEDSTATUSCODES
+- NO-SOLICITING
+- PIPELINING
+- REQUIRETLS
+- SIZE 104857600
+- SMTPUTF8
+- STARTTLS