To increase a mailbox quota in cPanel, go to Email Accounts, find the account, click Manage, and change the Storage Quota value. The change takes effect immediately.
If your business email stopped receiving messages or you got a "mailbox full" alert, the almost-always culprit is a storage quota that has been exceeded. This guide shows you how to fix it in minutes from your hosting control panel.
What Is a Mailbox Quota and Why Does It Matter?
A quota is the maximum disk space a single email account is allowed to use. Once that limit is hit, the mail server rejects incoming messages and senders receive a bounce with an error code like 452 4.2.2.
This usually happens for one of three reasons:
- The initial quota was set too low (for example, 250 MB for a high-volume account).
- Old emails and large attachments are never deleted.
- The account has been accumulating messages for years without any cleanup.
The fix may be to increase the quota, clean the mailbox, or both. Start by increasing the quota so email starts flowing again right away.
Steps to Increase Quota in cPanel
This process applies to any hosting account running cPanel version 78 or later, which is standard on the vast majority of providers.
1. Log in to cPanel
Go to yourdomain.com/cpanel (or the URL your host gave you) and enter your username and password. If you've forgotten them, check your hosting welcome email.
2. Open Email Accounts
On the cPanel home screen, find the Email section and click Email Accounts. You'll see a list of all active accounts on your domain.
3. Find the Account and Click Manage
Locate the affected address and click the Manage button on the right. A page with the full account settings will open.
4. Adjust the Storage Quota
Scroll down to the Storage Quota section. You'll see two options:
- Unlimited — no cap. Useful if your hosting plan allows it and you trust the user to manage their own mailbox.
- Custom (MB) — type the number of megabytes you want to assign. 1,024 MB = 1 GB.
For most moderately active business accounts, 1,000–2,000 MB (1–2 GB) is plenty. If the user handles many large attachments, consider 5,000 MB or more.
5. Save the Changes
Click Update Email Settings. The change is instant; the mailbox can now accept new messages.
Increasing Quota from WHM (Resellers and Admins)
If you manage multiple accounts through WHM (Web Host Manager), you can adjust quotas in bulk or update the limits for an entire hosting package.
- In WHM, go to Account Functions > Modify an Account.
- Update the Mail Quota field for the specific account.
- Or go to Packages > Edit a Package to set the default quota applied to all new accounts under that plan.
Keep in mind that the space available in WHM is capped by the server's total disk. You can't allocate more than physically exists.
What to Do After Increasing the Quota
Increasing the quota fixes the immediate problem, but if the mailbox hit 100% it's a good idea to do a cleanup so it doesn't fill up again soon.
Clean Up via Webmail
Log into Webmail (usually at webmail.yourdomain.com) and delete emails with large attachments. In Roundcube you can sort by size by clicking the size column header.
Empty the Trash Folder
Many users delete emails but forget to empty the Trash folder, which still counts against the quota.
Set a Retention Policy
Configure your email client (Outlook, Thunderbird, Apple Mail) to automatically purge deleted messages every 30 days. This prevents silent accumulation over time.
Checking Current Storage Usage
To see how much space each account is using before adjusting quotas, go to Email Accounts in cPanel and check the Storage Usage column. You can also see total disk usage under Disk Usage on the cPanel home screen.
| Usage Profile | Recommended Quota |
|---|---|
| Informational / transactional (low volume) | 250–500 MB |
| Active business account (daily use) | 1–2 GB |
| Heavy attachment or file use | 3–5 GB |
| Executive / high-activity account | 5–10 GB or unlimited |
If your hosting plan doesn't have enough disk space to accommodate the quotas you need, it may be time to upgrade. elenlace.com offers business email plans with generous storage at prices designed for small and mid-sized businesses.
For more tips on managing your corporate email, visit our business email section for updated guides and comparisons.
Key Takeaways
- A mailbox quota limits the disk space available to an email account; when exhausted, incoming messages bounce.
- From Email Accounts > Manage in cPanel you can adjust the quota in seconds.
- You can set a custom value (in MB) or choose "Unlimited" if your hosting plan allows it.
- After increasing the quota, clean out attachments and empty the trash to prevent the mailbox from filling again.
- If your overall hosting disk space is insufficient, consider upgrading to a plan with more storage capacity.
Is your hosting plan too tight on space, or does cPanel feel overwhelming? Reach out at elenlace.com and we'll help you move to an email plan that fits your business.
FAQ
Can I set unlimited quota for all my accounts?
Yes, as long as your hosting plan has enough total disk space. "Unlimited" quota for an individual account means it can grow up to the global plan limit — not that storage is truly infinite. Only assign unlimited quota to active accounts to avoid one user consuming all available disk space.
How long does the quota change take to apply?
The change is instant in cPanel. The server starts accepting new messages as soon as you save the settings. No restart or DNS propagation is needed.
What happens to bounced emails sent while the mailbox was full?
Bounced messages will not arrive automatically. Senders need to resend them. This is why it's important to act quickly as soon as you receive a mailbox-full alert.
Can I change the quota from my phone?
Yes. cPanel's interface is mobile-responsive. Open yourdomain.com/cpanel in your phone's browser and the steps are identical. Some hosting providers also offer a dedicated cPanel mobile app.
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