I’ve used Language Transfer with good success. Don’t even need to sign up, you can just go, click on a course and start streaming lessons. You can also download them locally.
https://www.languagetransfer.org/free-courses-1
The idea is to create rules that help you “transfer” words from the source language into the target language, hence, “Language Transfer”.
For example, going from English to Spanish: Words in English that end in ation, will end in acion in Spanish.
Confirmation -> Confirmación Conversation -> Conversación
Further, words following this rule are “ar” verbs. Confirmation -> Confirmación -> confirmar
Another one is words ending in al, which came to Spanish and English via Arabic… are the same. Just said with an accent.
Normal -> Normal Formal -> Formal
A few rules might get you a few hundred words. And while some words might be more formal that how something is typically said, you should still be understood.
They’re completely donation based, ad-free, and no sign-up required.
Currently using Stalwart after about a decade of using iRedMail. Stalwart’s setup was such a breeze; I let out an audible laugh/noise when the install completed in the blink of an eye and had all the DKIM, DMARC, SPF, etc. settings available for config.
Making some nice improvements with each release too, proper user management, etc. Definitely a fan. Looking forward to when they support CalDAV and CardDAV.