Emails, or e-mails, were messages distributed by electronic means from one computer to another via a network, typically the Internet. (PROSE: The Twilight Streets)
On Earth, such technology was used as early as of the 2000s, (TV: Rose) and was still common as of 2040. (PROSE: Outsourcing)
Keri once received a spam email from Galaxy Five's Readers Digest. (PROSE: Big Bang Generation)
During the Atraxi incident in 2008, email was one of the methods suggested by the Eleventh Doctor to Jeff Angelo to spread his computer virus across the world. (TV: The Eleventh Hour)
Ianto Jones' email address was iantojones@torchwood.co.uk. (AUDIO: Fall to Earth)
Vivien Rook designed an email to be automatically sent to Torchwood if she failed to return to her desk at 10:30pm. Jack Harkness later retrieved the message, finding it contained information on Harold Saxon's Archangel Network. (TV: The Sound of Drums)
The Twelfth Doctor's sonic sunglasses could send and receive emails. A virtual version of the Doctor used this to send the real Doctor a recording of the Monks' simulation called Extremis. (TV: Extremis)