[CentOS] Which is better? Microsoft Exchange 2016 or Linux-based SMTP Servers?

> [...] People want their phone to
> remind them of their appointments [...]

It's a generalization. Not valid for all people.

Maybe SOME people want their phone to remind them of their appointsments.

My appointments are synchronized from owncloud to Thunderbird and to 
many (LineageOS-based) smartphones and tablets and >>I<< do NOT want to 
be reminded on the smartphones and tablets, but ONLY on Thunderbird 
desktop client.

Regards,

Meikel