Edit C:\ProgramData\MailArchiva\Tomcat\conf\server.xml (Windows)
Edit /var/opt/mailarchiva/tomcat/conf/server.xml (Linux)
...and ensure the Host tag is as follows:
Afterwards, restart MailArchiva for changes to take effect.
See https://help.mailarchiva.com/upgradeissues for the complete set of steps to upgrade to V8.11.
Notably, 1) set autoDeploy and unpackWARs to true 2) change the keyPass attribute to keystorePass in Tomcat connector 3) Include secretRequired="false" in AJP connector