Three Ireland is one of the latest service providers in Ireland to provide Rich Communications Services (RCS) messaging to its customers. RCS is basically iMessage for Android, and it allows you to communicate with other device-owners on RCS-enabled networks over Wi-Fi or mobile data. Messages sent should be entirely free, and they’ll integrate with your Google Messages application when sending messages to people. In other words, they act exactly like regular SMS and MMS messages. It also allows you to enable typing indicators and read receipts in your conversations while giving you more advanced features such as emoji reactions and sticker replies.
You don’t need to enable anything to use RCS – simply download the Google Messages application, go to its settings, and tap “chat features”. If it says “Connected” like in the screenshot above, then that means it is enabled and you can message other people who also have it.
Currently, Vodafone Ireland customers also have RCS, though GoMo and Eir do not. There is sadly nothing you can do to enable the feature, except for pestering your mobile operator to support it. For markets where SMS is used a lot, it’s an absolute game-changer. Admittedly, I imagine its demand in Ireland is not that high, given the proliferation of alternative messaging platforms such as Facebook Messenger and WhatsApp
Source
https://www.irishtech.ie/rcs-three-ireland-launched/
