Creating a Persona in Zimbra webmail

Users with aliases (like @hers.com addresses) may have to set up a persona in their webmail account for using that alias when they send email.
For security reasons Zimbra 10 will only allow sending from addresses that are hosted on the same Zimbra server.

• Go to HIS webmail: https://securemail.his.com
• Go to Preferences > Accounts (or Settings > Accounts in the modern UI).
• Click Add Persona.
• Enter a name for the persona and configure the "From" name and email address, which will appear in outgoing messages.
• If needed, set a "Reply-to" address and specify conditions under which the persona should be used by default
• Click on Save on the top left side of the page to save the persona.

You should be able to send with the alias address after that.