Hello Brad,
You can customize the email subject by modifying the language file which is located in /language/en-GB/en-GB.com_easyblog.ini and locate the codes below:
COM_EASYBLOG_EMAIL_TITLE_NEW_BLOG_ADDED_WITH_TITLE="New blog post - %1s"
As for personalizing the contents of the email, what you can do is to add the code below into the file /administrator/components/com_easyblog/tables/blog.php and at line 1086 add the codes below:
$category = EasyBlogHelper::getTable( 'category' );
$category->load( $this->category_id );
$data[ 'blogCategory' ] = $category->title;
Then in your e-mail template, add the code below to output the category title
<?php echo $blogCategory;?>