I don't think it's possible, or at least not in the way you're thinking. Encoding a video with lossless flags usually results in a file size bigger or about the same as the source, and on top of that it takes a long time to actually do the encode.
Video is already highly compressed.
But for sure you can tinker around with ffmpeg (FOSS) & see how it goes for you. I've done it in the past just for kicks since some of the common video codec encoders do have lossless flags but it really wasn't worth the effort.
EDIT: That's just the video in the file, you also have to contend with the audio. That's a bit easier if you just want to use ffmpeg to dump everything into FLAC but again, I don't think you're saving much hard drive space if any.
Usually it's just badly coded apps/websites that only whitelisted some of the main domains e.g. most vanity domains don't make it through. Or sometimes there are apps/websites that purposely block your domain if the admins think it's too spammy or whatever.
If your current email provider allows you to use their own domains as an alias that's one way to sidestep the issue e.g. you'd end up with [something]@[youremailprovider].com --> [name]@[name].rocks
I have Fastmail & they have a ton of their own internal domains so that's one way I sidestep that issue. It's pretty common among most/all email providers when you bring your own domain e.g. pretty sure Proton can do the same thing. Once you have your own domain you can make up any [alias]@[yourdomain] you like or just use the provider's as a front facing alias [alias]@[youremailprovider] --> [anything]@[yourdomain].