Google is set to start warning Gmail users when they receive an unencrypted email.
While email encryption is on the rise, it is still far from ubiquitous, Gmail warned, citing a study it carried out along with the University of Michigan and the University of Illinois.
Its findings showed that 61 per cent of inbound emails are now encrypted, up from just 33 per cent in December 2013, when the study began.
However, some countries are stripping emails of their encryption as they come in, Gmail's engineers warned.
In a blog post, Gmail's anti-fraud and abuse research expert, Elie Bursztein, and security engineering lead, Nicolas Lidzborski, wrote: "We found regions of the internet actively preventing message encryption by tampering with requests to initiate SSL connections."
An infographic of the latest research, courtesy of Gmail
Meanwhile, the research uncovered malicious DNS servers that publish bogus routing information to email servers looking for Gmail, allowing attackers to censor or alter emails before they reach recipients.
"While these threats do not affect Gmail to Gmail communication, they may affect messaging between providers," Bursztein and Lidzborski said.
These threats have led Gmail to work on a warning system that alerts users when they receive unencrypted mail.
"To notify our users of potential dangers, we are developing in-product warnings for Gmail users that will display when they receive a message through a non-encrypted connection. These warnings will begin to roll-out in the coming months," confirmed the bloggers.
