It's not an issue, it's the desired behavior
We don't want to use amavis with getmail: this choice has been taken to avoid any bounce-related problem.
I know, but in this case NethServer is not a mail server and I don't see any real reason to use it in this way.
If you have a remote mail server, you can access it with any existing mail client (roundcybe includes).
Also, IMHO, you should apply the filtering in the original mail server since is much more efficient then getmail.
Beside this, you can also try to implement attachments removal using altermime as external filter for getmail.
We don't have plans to do it right now, and I don't even now if it can work.
Amavis is used when the machine is a real mail server and receives mails using SMTP protocol.
Virus check is done using clamscan. If a virus is found, the mail is dropped.
No, NS is a fully-featured SMTP/IMAP mail server.
You need to use Sophos client adsexternal filter for getmail, in the same way we do with clamscan.