It’s funny…
I have a domain with several associated aliases that hang from it, i.e. I have a main domain e.g. myhome.com and as alias server I have myhome.net, myhome.org, myhome.biz, etc…
Well, when I enter the webmail or usermin I see as default domain from which the mail is sent @myhome.biz for example, and I do not see how to change it, and the main is .com and the others are all Alias server that hang from this, but always sent from .biz.
How can I fix it?
Webmail, you mean roundcude? In roundcube in settings you have Identities and you can set a default address there.
With usermin the default is mapped to the domain you login the at port 20000. So login at https://domain.com:2000/something@domain.com with be the default address.
P.S. roundcude probably the same but you have the extra Identities in settings.