The security vendor CloudMask has launched a free tool for securing emails and attachments in Gmail, aimed at consumers and small and medium enterprises (SMEs).
Currently in beta testing, the service allows you to encrypt messages from draft stage to when they are opened by the recipient, working through a Firefox addon.
Wael Aggan, chief executive at CloudMask, said: "We want to give users full control over managing their sensitive data. Normal email messages and attachments can be intercepted or hacked before reaching the recipient, or even whilst they are sitting in your inbox."
"CloudMask encrypts emails at all stages from creation to consumption – even if it is stored as a draft. In addition, attachments in all formats including pictures will be masked from everyone but the recipient."
Once signed up for the service, a user requires both a password and digital key to decrypt and read their emails, with the key stored on a device such as a computer or USB.
This two-factor authentication means that a hacker cannot read encrypted documents even if they obtain the logins to the account, unless they have access to the device on which the key is stored.
However the secure messaging only works if both sender and recepient are signed up to the service.
Later versions of the software are intended to work across Outlook.com, Box and Google Drive and Salesforce, with functionality due to be rolled out across Internet Explorer and Google Chrome with three months.
"Communication and collaboration in the cloud is inevitable but has resulted in embarrassing moments for governments and celebrities alike," Aggan added.
"Data protection regulations will soon require businesses of all sizes to anonymise personal data in the cloud and there is very little out there to help them do this."