Remove the !important and it will not alter the the links you inserted with tags, like the readonline link.
When you also need to make changes to the readonline and unsubscribe links, Acymailing is assigning classes to these links, so you can use these to address your css.
You can't add specific classes to your links. You can however add html-id's to your blocks. You can use these to adress your css for a specific block.