Well, if all settings are correct, then it should work fine. DriveHQ email service supports standard SMTP/POP3/IMAP.
Please double check your settings. You can find very detailed step-by-step help at:
http://www.drivehq.com/email/
One very frequent problem is: you need to check "Outgoing emails require authentication" for sending emails using our service.
DriveHQ strictly forbids spamming. So if you cannot receive emails from some users, it's possible that their email servers have been blocked. In that case, please email us a copy of the bounced back email as an attachment, we will add their email servers to our allow list.