kmail is installed in Kubuntu out of the box, and it works fine. If I install kmail in Neon it doesn't properly work because it needs akonadi and others, but I don't know what the others are

So how should I install fully workable kmail in Neon?

I do not use kmail on my system. On attempting to install the programme there are 112 packages required as the install installes the pim suite of programmes.

You best bet might to to reinstall kmail using synaptic as this should pull in all the other packages.

iliav wrote:kmail is installed in Kubuntu out of the box, and it works fine. If I install kmail in Neon it doesn't properly work because it needs akonadi and others, but I don't know what the others are

So how should I install fully workable kmail in Neon?

Installing Kmail should also install all the akonadi parts it needs; for me it downloaded 35 mb of packages. It installed fine here for me, and ran as expected.
What specific error are you seeing? What did you install, specifically, and how did you install it?