always_bcc = backup
myorigin = $mydomain
The always bcc mail is sent to backup@$mydomain. This is how
Postfix has worked for the last four years.
If you want to have such mail delivered locally, then I suggest
that you specify:
always_bcc = backup@$myhostname
or something equivalent.
If you were redirecting the backup mail with a virtual map
Then perhaps something broke the virtual file as you upgraded to
a newer version of the Berkeley DB library, which is documented as
not compatible with itself in he RELEASE NOTES file.
There are about five million other ways in which you could have
received the backup mail locally, but I am not going to enumerate
all of them. I hope you understand that I have other things to do.