Office 2011 for MacBook Pro

I'm using MacBook Pro and using Outlook 2011 for mac and use Imap.

I receive e-mail, but suddenly I cannot reply, reply all or forward any e-mail anymore, which I could before. 

1. I checked all the outgoing mail settings, port is 587  
2. I deleted my account and configured again
3. I also tried pop configuration. None of them helped me to send again e-mail.

Thanks for your help!

Best,

Orkide