exim -bp | exiqsumm
The output consists of one line for each domain that has messages waiting for it, as in the following example:
3 2322 74m 66m msn.com.example
This lists the number of messages for the domain, their total volume, and the length of time that the oldest and the newest messages have been waiting. By default the output is sorted on the domain name, but exiqsumm has the options -a and -c, which cause the output to be sorted by oldest message and by count of messages, respectively.
The output of exim -bp contains the original addresses in the message, so this also applies to the output from exiqsumm. No domains from addresses generated by aliasing or forwarding are included (unless the "one_time" option of the redirect router has been used to convert them into 'top level' addresses).