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Learn about the maximum email attachment size and storage capacity for mail accounts.
Email Account Limits
| Type | Max Mailbox Size | Max Attachment Size* |
|---|---|---|
| Mail Basic | 2 GB or 100,000 emails | 70 MB |
| Mail Business | 50 GB or 500,000 emails | 70 MB |
| Microsoft Exchange 2019 | 50 GB | 100 MB |
| Microsoft 365 Business Basic | 50 GB or 1 Million emails per folder | 150 MB when using Microsoft Outlook or 35 MB when using the Outlook Web App (OWA) |
| Microsoft 365 Business Standard | 50 GB or 1 Million emails per folder | 150 MB when using Microsoft Outlook or 35 MB when using the Outlook Web App (OWA) |
Please Note:
If the maximum mailbox size is exceeded, the account will no longer be able to receive incoming email. The sender will receive an email notification explaining this as the reason why the email was not able to be sent.
* The limits above are applicable when sending from an IONOS mail account to another IONOS mail account of the same type. Some email providers will reject an email if the file size exceeds their maximum file size, which could potentially be lower than the limit imposed by IONOS. If so, you will receive a bounceback message from that email provider informing you that the mail was not delivered because the attachment is too large.
Checking Your Email Storage Usage
Guided Steps
- Log in to your IONOS account and click on the Email tile.
- If necessary, select the appropriate contract containing the email address you want to check.
- Next to the desired email account, From the Tasks column, click the gear icon and select Settings.
Now you can see the account's current usage and maximum size allowable under Email storage.
Webmail Guided Steps
- Log in to Webmail.
Below the Inbox and mail folders you will see Mail quota, showing the account's current usage and maximum size allowable.