The bug is "deactivated", if it's activated : it's a plugin issue, but not activated : it's a LimeSurvey issue in my point of view

I think extend PluginBase is the good solution.

But it was disable at 2.63 ? No ?

https://github.com/SondagesPro/LS-sendMailAjax/commit/d5438c107c737af9b0e9388e9a5ac6d99570e940

OK : https://github.com/LimeSurvey/LimeSurvey/blob/master/application/core/PluginBase.php is currently in 3.0
And in 2.67 too
https://github.com/LimeSurvey/LimeSurvey/commit/e8d2a9ecf360071786570e3e06b3843b59049e92#diff-5a91a12f23c22838ec1eb101856b1f1b

BUT : i's not in API : https://github.com/LimeSurvey/LimeSurvey/commit/212a0e73e039e645faf8d91dc371553768ecb0e1#commitcomment-20983028

About the orginal issue , i think we need a plugin.xml/plugin.json/… … anything

With an array
'compatibility' =>(
'min'=>
'max'=>
)

For starting, and add more extra option/information (licence , homepage etc …) after.

I can take it if OK.

Current solution : 2.72+3.0 compatible plugins.
change 'ls\pluginmanager\PluginBase' into 'PluginBase'

no retro compatibility for plugins

@LouisGac : i understand the no retro compatibility, the point is
«Don't load old plugin that can broke LimeSurvey»

You have a 2.63 plugin, you use comfortupdate to don't have to go to FTP
You update to 3.8 …

Nothing to do : you must go to FTP …