Email sending is supported in Gekkota. This is the list of supported authentications:
GSSAPI
CRAM-MD5
NTLM
MSN
PLAIN (1)
LOGIN (1)
(1) These authentications are not active by default with a Google account. To activate them, go in Google account parameters menu, and activate the option "Allowing less secure apps to access your account"
The authentications below (used by example by Google) are not supported:
XOAUTH2
PLAIN-CLIENTTOKEN
OAUTHBEARER
XOAUTH
NOTE FOR MS-EXCHANGE 365 ACCOUNT
Given the SSL negociation is done afterwards, the URL has to follow the scheme smtp:// (and not smtps://) ex: smtp://smtp.office365.com:587