How do you send a message through xbox live on the website?

No, you simply need to install the xbox app. Once you login the app you can send messages and also join or start a party chat. 

I have to download an app because the website is incapable of sending messages? lol wow even Sony figured this out. Nintendo is going to have a better online infrastructure by the end of this generation.  What a trainwreck.

How do you send messages via the XBox Website as I don't know how to now and it's really annoying!

As far as I know, you can do it by going to your own profile and it used to say (It probably still does somewhere) where your XBox Messages are. I am however using the XBox Website on my Mac / PC and sometimes use Google Translate to communicate with other gamers this way.

Apparently that is no longer an option even though it used to be. How did MS botch this? You're supposed to add features not remove them. SMH.

Because it avoids spam 

People can do random accounts then spam users with msgs with impunity

If they get banned they just create an new account

And yes spam is a problem on all consoles

You can use the android app or the windows. 10 app you know

Nintendo is in beta for online services if you think nintendo has a better service here news for ya its NOT

they dont have many services and nowhere near the apps and services that sony and ms users enjoy and for god sake you do know there is an ios app right ?

They cant even get deals done

Vlc netflix

Again there is no apps

And party chat is in no condition to be bragging about

Fyi nintendo is focusing on nintendo switch pro or 2 as they mentioned they have slowed down their online offerings including the free snes and nes offerings 

You used to be able to send a XBL message thru the website, however MS/Xbox decided to go another direction.

It has nothing to do with SPAM, MS/Xbox simply feel that the "Xbox Experience" would be better all tied to one app!

I think it was the wrong move, but That's just my opinion....Hope this helps.