My understanding is that this was an optional feature, and turned off by default - a user wanting to use this would need to enable it manually.

If a user turns on a feature to request favicons for received mail, it therefore seems logical that the app has to retrieve favicons. Doing direct retrieval is likely less damaging to privacy than using a central favicon retrieval server.

I use FairEmail so I just checked: Display Favicons is disabled by default and there's a note below the setting that says "there might be a privacy risk" and links to https://en.wikipedia.org/wiki/Favicon

Agreed, 1) it's not sharing contacts, 2) it only pings those domains if you enable the optional feature. This is exactly how I'd want the app to behave, and I honestly can't think of a better way to handle it.

Maybe caching the favicons on a server hosted by the app creator so that no matter what domain the app looks up, it looks like it's contacting FairEmail.

But in that case, the app creator would have a list of domains which I think is objectively worse from a privacy perspective...

I'm honestly a bit annoyed that OP is the top comment on HN when it exaggerates the impact of this feature.

OP here. You are right.