Hi there. I'm a relatively new user to Marketo.
Late on Friday, I discovered that three lists I previously created (and successfully mailed to) had become corrupted in some way, and all had reduced in size from 50-90%. I tried to figure out why a list of 200 would reduce to 11.
Giving up, I decided to re-import the exact same lists I'd successfully imported a month earlier. The lists appeared to be importing correctly (the import preview window showed that the sample records were matching correctly to First Name, Last Name and Email address --- the only three fields I was importing).
When I viewed the resulting list, no email addresses appeared for the records. I tried manually recreating the CSV files and remporting to Marketo, and this also imported successfully, but without any email addresses. Marketo is not supposed to support this.
If anyone else is experiencing this challenge, please let me know. I'm using the same browser from the same computer that I last used to successfully import this same list. (Chrome Version 25.0.1364.160 on Mac OS 10.8.2). I also retried it on Safari and Firefox with the same results.