Google recommends no more than 100 outbound links per page of a website. As for IBL's, directory submissions dont all get authorised at once, so you could submit thousands and they would filter in over two months or more.

My advice is to not worry about volume. It is the relevance, site authority and keyword anchor text in those links that is vital to your success. You can do a strong backlink building campaign without ever having to worry about Google thinking your linkbuilding is unnatural. They are really on the look out for the link farms and automated link exchanges who allocate out thousands of random links to a site, all suddenly appearing in a few days etc.

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