In many cases tool/library recommendation questions can be rephrased to focus on the actual problem being solved instead of being focused on getting a bunch of names/links to tools/libraries.
By asking for a tool/library, you are likely to only get answers containing the name and a link to the product, with very few other details, however by asking about the problem you are trying to solve, you can get a full solution to your problem, which may or may not be accompanied by an existing tool or library link.
It should also be noted that product requests which are detailed and specific enough to elicit the product for the solution are OK. In these cases, enough details have to be provided that the community can easily judge a "correct" answer, instead of only having the votes based on what is popular.
But in regards to your two specific questions:
Dummy SMTP Server for testing apps that send email
I think this question just needs a title change from "Dummy SMTP Server for testing apps that send email" to "How do you test sending email?".
The current title is asking for a product recommendation, which encourages users with any product or library that meets your criteria in an answer. The 2nd title focuses on your actual problem, which encourages people to post a solution to the problem instead of just a link to a product or library.
The change in title will also make the 2nd highest voted answer correct, since it is pointing out a setting in web.config that you can modify instead of giving you the name of a product you could use for testing emails.
The rest seems OK, since you're fairly specific about your setup and what sort of tests you want to run, although you might want to change the question at the end from "But surely such a tool already exists?" to be a statement instead of a question, such as "Perhaps a tool already exists for this".
SQL Client for Mac OS X that works with MS SQL Server
For this one, I'd suggest the same thing: change your title to focus on the problem you're trying to solve instead of asking for a product, such as "How can I work with MSSQLServer from Mac OS X using a GUI?"
It might also help to make sure your specific requirements (color coding, result set grid, etc) stand out a bit more, such as putting them in bullet points, so users know you're looking for those specific features in the answers, and can judge them accordingly.
Other than that I can't think of much else since you were fairly specific about what system you're running on and what specifics you were looking for, and a quick glance through the answers is only showing a handful of answers highly voted.
I've voted to reopen both questions, as I think they are good ones (the dummy SMTP one has helped me in the past), but I'd still encourage you to edit them slightly so they focus on the problem you're trying to solve instead of asking for a product recommendation, as that will help get more reopen votes and help prevent them from getting re-closed in the future.