You can export data from Mailfence web-interface using following two ways:

Create a Backup:

1. Settings

2. Account -> Back-up:

3. Click on Export after choosing an element that you want

The restriction on backup file size is applied for performance reasons e.g., for documents: up to 250 MB of data. If you need to backup large volume of data, please use external clients e.g., CardDAV/EAS client for contacts, CalDAV/EAS client for calendar events, WebDAV client for documents, and IMAP client for emails.

Export selected items

For exporting a specific email:

• Right-click on the message in the message list panel -> Archive -> Download.
  Please that this option is not available in Free subscription.

For exporting a specific document:

• Right-click on the document -> Download.

For exporting a specific calendar event:

• Right-click on the calendar event -> Export.

Check our documentation to learn how to export several or all the events at the same time.

For exporting a specific contact:

• Right-click on the contact -> Export (vCard).

For exporting your OpenPGP keypair(s)/other public keys:

• Please check this article.