Microsoft has announced plans to double the capacity of its Office 365 mailbox to 50GB.

The expansion will be free of cost, and it follows tripling file storage capacity on SkyDrive Pro earlier this week.

According to the company, the doubling of mailbox storage is part of its plan to deliver better mailbox service to its Office 365 customers.

The increase affects customers using Exchange Online and Office 365 service plans including Exchange Online Plan 1, Office 365 Small Business, Midsize Business, Enterprise E1, Government G1, and Education A1.

Additionally, the company has increased the size of shared mailboxes and resource mailboxes – both increasing to 10GB in order to help users work more productively.

The increase in storage capacity is effective immediately and is expected to continue through to November this year.

Microsoft said that Kiosk user mailboxes have been doubled in size from 1GB to 2GB.