When replying to emails, Protonmail and many other clients detect the existing "Re:" prefix in the subject, and don't add a new one to prevent the "Re: Re: Re: ..." mess.

This is fine in English, but other languages use different prefixes.

For example, the Finnish localization of Outlook sends its replies with "VS:", but Protonmail doesn't understand that prefix. This causes email threads with people who use Outlook to look like this:

-> "Original Title"
<- "Re: Original Title"
-> "VS: Original Title"
<- "Re: VS: Original Title"
-> "VS: VS: Original Title"
<- "Re: VS: VS: Original Title"
-> "VS: VS: VS: Original Title"
etc...

Please add a setting that allows the user to customize the list of prefixes that should be stripped from the subject when replying.