I think that another question might be "How can I get people to put in real email addresses and not disposable ones?"
But, in answer to your question: If you send a few (legitimate - not spam) emails to a recipient, and they all bounce, then that's probably a disposable one that expired.
If your question is about detecting services like mailinator.com, 10minutemail, ... this could be the service you are looking for: http://www.block-disposable-email.com
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[ 5.1 ms ] story [ 9.2 ms ] threadBut, in answer to your question: If you send a few (legitimate - not spam) emails to a recipient, and they all bounce, then that's probably a disposable one that expired.