Recently there are increasing number of people having trouble in adding their Gmail/Yahoo account on PS Vita. It seems that the issue occurs with firmware such as 3.01 and 3.18, while it is fine with higher firmware(3.51, 3.52).
When users adding gmail or yahoo account to Vita, there is an arror code: C2-14393-0. Some users delete the gmail account and re-login account back, but them failed. However, the same gmail account can load on Vita3.51 and 3.52. Apparently, there is a problem with email app on older PS Vita firmwares.
It is unclear if the app is being blocked at the Sony level, or the mail providers. Many user with older PS Vita firmwares have email account to run email-based Vita hacks.
There is still no visible solution with this issue. If Sony attempt to block hacking, there might be no solution in the futures. But users reported that other email providers such as gmx.com can access to email app with older PS Vita firmware, the current recommendation is to try and create an email account with other providers except gmail and yahoo.