Don’t be surprised if your email list reduces by 30% each year, as email addresses become invalid. Expect a hard bounce for rate of between 2% and 6% for each broadcast.
One of the most neglected aspects of self-publishing is proofing and editing copy. The world is full of people who write and publish their own content (myself included, as is evident with this very piece) and there is a wealth of un-proofed content, full of errors and inconsistencies.
I am guilty of not re-reading my own copy before publishing it, some of the time, but even when I do, author blindness will mean I miss some problems.
Here is a checklist for writers, to help you ensure your quantity is matched by quality.