There is a new pull request by nothien against master on the mblaze repository

https://github.com/nothien/mblaze master
https://github.com/leahneukirchen/mblaze/pull/209

mgenmid: add option -d for custom domain
In my setup, I use mblaze across multiple mailboxes, each with different addresses and domains, which they provide through mailbox-local configuration files.  I needed this option in order to select the domain programmatically.

A patch file from https://github.com/leahneukirchen/mblaze/pull/209.patch is attached