Marketo's reports are more intented to give a complete overview with numbers showing delivered, hard bounced, soft bounced, etc. However, you can see what your performance is by domain by using Smart Lists.
Navigate to Lead Database, and create a new Smart List. Using the filters, "Was sent mail - <email name>", and "Email address - contains - yahoo", you can see how many leads were sent a particular mail that had "yahoo" in the address. You can get further granularity by using the "Was Delivered Email" or "Not Was Delivered Email" filters instead of the "Was Sent Email" filter, and see deliveries or bounces. Try using different filters to get different results!
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