HTC seems to have forgotten about its sole entrant into the "phablet" market - they haven't released anything as large as the 5.9-inch One Max since its debut way back in 2013. But presumably the people who own it still like it, or at least use it, so the news that HTC is finally updating the device to Android 5.0 should be welcome. Numerous users have started receiving the Lollipop OTA as evidenced by posts to Twitter and XDA-Developers.
— Valerio Nebuloni (@ValerioNebuloni) June 17, 2015
At the moment it looks like the release is limited to European and Asian territories: so far owners in Poland, the Czech Republic, France, and HTC's home country Taiwan have reported that they've gotten the OTA alert on their phones. That probably means that the company is working its way through all the localized versions of the international model of the One Max. This is build number 4.13.401.7, coming in at just over 760MB.
The One Max was sold on Sprint, AT&T, and Verizon in the US, and the manufacturer will probably want to update all of those versions... eventually. As always, the verification process and custom builds for the carriers will probably take weeks or months. In the meantime, several intrepid posters on XDA have ported the update to other models - check out the source link if you're feeling brave.