# Email Solution: Frequently Asked Questions

  
This article addresses the most common questions regarding our business email solution. For quick navigation, questions are grouped by topic.

<span>**Account Management**</span>

1. **Why can’t I add a domain to the email solution?**
    
    You may see the error “Invalid owner handle!” when adding a domain.
    
    \- If the domain is registered with Openprovider, the handle you use when adding the domain must match the domain’s registrant handle. If they don’t match, the error appears.  
    \- If the domain is with another provider, this rule does not apply. You can use any handle under your account.
2. **“An unknown error has occurred” appears when creating an email account. Why?**
    
    This error happens because no domain has been added yet. At least one domain must be added before you can create an email with the domain.

<span>**Storage and Limits**</span>

1. **How much storage is included per email account? Are there any restrictions?**
    
    Each email account includes 15GB of storage by default, which can be increased if needed.
    
    \- Additional storage is available in 5GB increments for $0.25 per month, based on your requirements.  
    \- You can create multiple separate email accounts, each with 15GB storage (and independent upgrades). Each account is billed separately.
2. **Can the mailbox capacity be increased beyond 15GB?**
    
    Yes, you can increase mailbox storage in steps of 5GB, up to a maximum of 100GB per mailbox.
3. **Is it possible to downgrade mailbox capacity/quota?**
    
    Yes, this is possible. However, there is no direct automated option to do this from your end. If you would like to downgrade email account(s), please reach out to your [account manager](mailto:accounts@openprovider.nl).
4. **How large is the standard mailbox?**
    
    A standard mailbox is 15GB.
5. **Do you back up individual email accounts?**
    
    Backups are available for the entire server, not for individual accounts. Individual backups are not offered. However, if there is a server issue or data loss caused by us, we will restore emails for all users.

<span>**Mailbox Usage and Sending Limits**</span>

1. **How many emails can I send per hour?**
    
    Each mailbox can send up to 300 emails per day, with no hourly sending limit. These limits are in place to prevent abuse. If a higher limit is needed for legitimate use cases, please share your requirements with our support team for review.
2. **Is there a domain-wide sending limit?**
    
    Yes, all mailboxes under the same domain have a combined limit of 5,000 emails per day.  
      
    Example: If you have the following mailboxes:
    
    \- <info@mywebsite.com>  
    \- <help@mywebsite.com>  
    \- <hr@yourwebsite.com>
    
    Each can send 300 emails per day, no hourly restriction. However, in total, all addresses under [\*@mywebsite.com](*@mywebsite.com) cannot exceed 5,000 emails sent per day.
3. **Are there limits on how large email attachments can be?**
    
    Yes, attachments can be up to 20MB in size for sending via email.
4. **Can the user have multiple mailboxes on the same domain?**
    
    Yes, the users can have multiple mailboxes on the same domain.
5. **Why emails don't work for subdomains?**
    
    Currently, we don't support emails for subdomains.

<span>**Features and Customization**</span>

1. **What is Webmail?**
    
    Webmail is an online service that allows users to access and manage their email accounts through a web browser. With the availability of the Internet, webmail users can access their accounts from any device using any web browser. They can send, receive, and organize emails directly on a web interface without the need for external software. Gmail, Hotmail, Yahoo, and Outlook are some of the most modern webmail services on the market.
    
    **Security:** Because webmail operates over the internet, security is essential. Webmail services use encryption to protect data during transmission and offer additional security features such as two-factor authentication (2FA) and spam filtering.
2. **Can I access calendars outside of the webmail interface? (e.g., via CalDAV)**
    
    Yes, our email service supports CalDAV, which lets you connect your calendar to apps that support it.
3. **Is it possible to customize the webmail interface?**
    
    The standard webmail interface cannot be customized. However, we do offer the option to provide a dedicated server where interface customization is possible.
4. **How does email forwarding work?**
    
    You can check this KB Article → [**Email Forwarding**](https://openprovider.help/books/email-solution/page/email-forwarding)

<span>**Additional Support**</span>

If your question is not answered here or if you need further assistance, please contact our support team at <support@openprovider.com>