exim -bp | grep "string" -A1 | awk {'print $3'}
Replace string with the email address, or domain you want to search for and delete.
Note that -A1 may not be needed. Grep will just search for string and 1 line after it. I had a problem with the string I was wanting to use was on the line below it
list all simple queues
queue simple print
Print queue that matches part of name
queue simple print where name~"John"
Example results
Flags: X - disabled, I - invalid, D - dynamic
0 name="John Smith" target=192.168.1.3/32 parent=none packet-marks="" priority=8/8 queue=sfq-up/sfq-down limit-at=0/0
max-limit=1M/10M burst-limit=0/0 burst-threshold=0/0 burst-time=0s/0s bucket-size=0.1/0.1 total-queue=default
Change max speed on queue for client name. The Upload is specified first.
queue simple set max-limit=10M/100M "John Smith"