If senders receive a bounce notification stating 550 5.2.2 Mailbox is full / Quota exceeded when emailing your domain, this guide explains why the error occurred, how incoming message retries work, and how to resolve the issue in under 60 seconds without losing emails.
1. How Email Quotas Work Under the Hood
When an external mail server (e.g., Gmail or Outlook) attempts to deliver an email to your domain, the Nyota Mail daemon checks your storage capacity before accepting the message payload:
EXTERNAL INCOMING EMAIL (sender@example.com)
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NYOTA INCOMING SMTP NODE CHECK
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┌────────────────────────────┴────────────────────────────┐
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[STORAGE CAPACITY AVAILABLE] [WORKSPACE QUOTA = 100%]
Message written to IMAP storage. SMTP node returns:
Delivered to inbox in < 1 second. 550 5.2.2 Mailbox quota exceeded.
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SENDER RETRY WINDOW
Sending server retries delivery
every few hours for 48–72 hours.The 48-Hour Sender Retry Window
When an email bounces with a quota error, most enterprise mail servers do not discard the message immediately. They place the email in an outbound retry queue and attempt redelivery periodically for 48 to 72 hours.
As soon as you expand your storage capacity or purge deleted items, queued messages will deliver successfully on the sender's next retry.
2. The Three Common Causes of Quota Errors
- Communal Storage Pool is 100% Full: The total storage consumed across all mailboxes on your custom domain has reached the limit of your purchased workspace entitlement.
- Individual Quota Cap Reached: A workspace administrator set a manual hard limit (e.g., 500 MB) on a specific mailbox, and that individual employee exceeded their cap while communal space remains available.
- Accumulated Trash & Spam Folders: Deleted emails with large attachments (PDFs, videos, zip archives) continue to consume disk storage until the Trash and Spam folders are physically emptied.
3. Step-by-Step Resolution Paths
Path A: Expand Workspace Communal Storage (Instant Resolution)
If your entire domain has reached capacity, expanding your pooled storage restores incoming email delivery across all accounts in seconds:
- Log in to the Nyota Mail Console.
- Under Domain Storage Overview, click "Expand Storage Pool".
- Select the amount of additional capacity needed in 1 GB increments (KES 50 / GB / month).
- Click "Confirm Purchase" to settle instantly via your Nyota Wallet, M-Pesa STK push, or card.
- Your storage pool updates immediately, and queued incoming messages will deliver on the next sender retry.
Path B: Adjust Individual Employee Quota Limits
If your workspace has available shared storage, but a specific user is bouncing with quota errors:
- Go to mailadmin.nyotaimara.com/mailboxes.
- Locate the affected employee's email address and click "Edit Quota".
- Increase their hard limit (e.g., from 1 GB to 5 GB) or select "Dynamic (Draw from Shared Pool)".
- Click "Save Settings".
Path C: Purge Deleted Items in Webmail (Free Resolution)
If you do not wish to purchase additional storage, employees can free up disk space immediately by purging deleted folders:
- Log in to Webmail at mail.nyotaimara.com.
- Right-click the Trash folder and select "Empty Trash".
- Right-click the Spam / Junk folder and select "Empty Junk".
- Sort your Sent and Archive folders by size to delete or download large historical attachments.
4. Automated Storage Alerts
To prevent unexpected quota bounces in the future, Nyota Mail sends automated email notifications to workspace administrators when domain storage crosses:
- 85% Capacity: Warning alert to review storage allocations.
- 95% Capacity: Urgent alert recommending a 1 GB storage expansion.
- 100% Capacity: Critical notification indicating incoming messages may be deferred.