Dovecot "User-Agent" equivalent

[Plutocrat]

Hi,

I was trying to debug an IMAP connection problem. The client accesses an account via webmail, mobile phone, and desktop. I was wondering if there was a way of determining which of these they were using at a given time. 

My googling turned up the following settings in the imap{} section:

protocol imap {
  imap_id_log = *
  imap_id_send = "name" * "version" *
}

... but setting these didn't seem to log any more information that I could use. 

Have I misunderstood the usage of these settings? Shouldn't they log a "user agent" type information in /var/log/dovecot.log ?

Or are there any other ways I can get information on the client? 

P.