I have a virtual server using the Plesk control panel. Everything is working fine with a few minor exceptions. One is that I cannot send emails through the webmail interface. Emails come in, can be picked up via Outlook, etc. Emails can be sent via Outlook through the server. When I access the webmail, incomming emails are there, can be read, deleted, etc. In most cases you can reply as well. However, although it seems that the email is sent, it never goes through. It is even in the sent mail folder like it went, but never arrives at the destination. Also, in some instances, I get an error when I try to send a message that reads, "There was an error sending your message: unable to add recipient [someone@somewhere.com]: Invalid response code received from server" when I know this is a valid address. Also, if I send a message to myself, I receive it.

Second, (and this is probably related to the first) mail forwarding or "redirecting" doesn't work.

Also, is there a way to add spell check? And a nicer webmail interface than Horde?