All my websites and even the SMTP server is unable to send an e-mail to an alias. It just errors out. Is there any way to correct this?
I actually figured this out. For those having the same problem. We use an external server for our domain registration and DNS settings. We were also using them for our e-mail forwards. However, when using ISPConfig to send outgoing mail to these forwards we needed to set these forwards within ISPConfig as well.