I have been unable to confirm this on an official LDS website, but Elder Tonini sent us the following:
"Missionaries are to write to their families each week and
are also authorized to communicate by email with friends, priesthood leaders,
and new converts. Mission presidents should allow sufficient time on
preparation day for missionaries to write emails and letters. While in the
mission field, missionaries should receive authorization from the mission
president before entering into communication, including via email, with
converts and others of the opposite gender within the mission boundaries (see
Missionary Handbook, 36–37)."
He explains that this means: "I
can now email basically whoever I want now. If anyone wants to email me, they can."
His email address is now included above the mission home address on the right-hand side of the blog.