Note: Per https://www.virtualmin.com/documentation/email/troubleshooting this is not a new problem
Domains used in documentation below
from firstname.lastname@example.org hosted on machine1.example01.com
to email@example.com (for test purposes also on machine1.example01.com
shows in recipient's mailbox as being sent from firstname.lastname@example.org (completely different domain)
this is consistent whether recipient is using Squirrelmail on host machine1.example01.com or a free email account from a provider whose name begins with Y and ends in !
Per https://www.virtualmin.com/node/8415, configurations
Path: Webmin > Usermin Configuation > Usermin Module Configuration > Read Mail
Section: User From addresses
Option: From: address Mapping File set to "/etc/postfix/virtual"
Option: Address mapping file format set to "Address to username(virtusertable)"
file /etc/postfix/virtual is world readable
Webmin: Networking > Network Configuration
Option: Hostname and DNS Client
hostname is some_name_not_in_dns.example01.com, name is NOT registered in example01.com's DNS records
Additional actions taken
Path: Options > Personal Information > Edit Advanced Identities
email address shows as email@example.com (another domain on machine1.example01.com )
Note: for domain example11.com squirrelmail was probably setup when logged into root at
Uninstalled Squirrelmail and reinstalled logged into root at
Logged into http://example11.com/squirrelmail/ as user_a.example11
Options > Personal Information > Edit Advanced Identities
show E-Mail Address as "firstname.lastname@example.org"
(some progress at least, mail is now coming from correct domain, username is still not in desired format)
Also, stopped and started Postfix, results did not change
What have I missed?