Server -> Mail -> Whitelist (broken)

[damienf]

I'm getting an error when trying to send from IMP (Horde) which says

"There was an error sending your message: unable to add recipient [********@yahoo.com]: Invalid response code received from server"

I have read up on this and thought I had to add a record to my whitelist. However when I go there in the control panel there is nothing but a white page. What should I do now?

 

[hardweb]

The problem is related to SMTP, read on this forum, you will find multiple solutions, one of them being to use sendmail instead.