Inbox: always let a trusted sender past spam, and files with a virus set aside

Two improvements to how Solstral handles what your mail server flags.

• Never treat as spam. Add an address or a company's domain in Settings ▸ Email ▸ Inboxes, for one inbox or all of them, or press Always allow… on a message in Spam. Their email skips the spam check from then on, as long as it proves it came from them (DMARC).
• Files with a virus are set aside, not lost. The email is kept; each attachment shows on the record as blocked and can't be opened, and your admins are told.