For the longest time we were seeing
javax.mail.NoSuchProviderException: No provider for smtptype exceptions. My searches told me that this was most likely because of either a mis-match between my mail.jar and activation.jar files or that I had duplicates of either. I was positive neither was the case. Finally, I removed the JAR files and the code still compiled. We must have had a duplicate after all. After putting together a Perl script to search all the JARs on my classpath, I found that the google-api.jar was in fact the culprit. It includes both the mail and activiation frameworks. So for anyone else who happens to come across this same problem and then subsequently comes across this page (i.e. nobody), now you know what to do.