What programs or web services for checking the grammar of a language do you know?

Question

Spellchecking

All emails must be checked before being sent. It is advisable not only to check spelling, but also grammar.
I know that there are such services, for example, Grammarly. But they work in such a way that you put a plug-in in a browser or software, and it sends all the text for verification. It turns out that everything I write will be leaked (both passwords and personal correspondence), such telemetry does not suit me. I only need to check what I request, nothing more. Interested in software solutions for Linux or web services, the main condition is the absence of total telemetry. Spot check only. Is there such a thing?