Emails *should* be sent prior to the issuance of a BRP. However, a decision is given by email only when your application has been approved.
As @seagul has advised, DX are the courier responsible for delivering BRPs. Your decision letter should follow soon after, but by Royal Mail.
Application Type: Settlement, Fiancé
Application Date: 26 June 2019
Decision Date: 29 August 2019
Application Type: FLR(M)
Application Date: 23 October 2019
Decision Date: 28 October 2019