I am a Board member of a charitable organization. We have dozens of volunteers, many of whom have email accounts running on our hosted domain, but interfaced through their own hardware. Some are very infrequent users, and the funds available to support their overhead are minimal.
These volunteers interface with donors and other external parties, and our organization would like to have a comprehensive, failsafe, unassailable backup and record of all (each and every without exception) email RECEIVED AND SENT from all users on our domain. WE DO NOT WANT THE VOLUNTEERS TO BE ABLE TO "CONTROL" OUR BACKUP -- that is, if it's received, we want an exact record of it (even if the user deletes it off of her interface) and if it's sent, we want our own record of exactly what was sent (even if the user deletes it from her sent box) -- to whom, when, subject, content, bccs, etc. (if we can't get the list of bcc recipients, we can live it, so long as we know what content was sent).
We currently use a POP-based interface (which lacks this backup capability -- particularly for sent emails -- as far as we know). We have been advised to switch to IMAP; if we undertake the switch, we want to make sure we accomplish our "unassailable backup" objective at a reasonable cost for our organization.
Our hosting provider indicates that if we switch to IMAP, on their server, they can setup an auto-forward feature so that every incoming email to every user can be forwarded to a master inbox that is not linked to the users' inboxes, and therefore, the charity will have its own copy of every received email.
However, the hosting provider indicates that a similar type of functionality does not exist for outgoing mail.
Our volunteers frequently work offsite, so they are on their own computers, phones, etc., so we need this function to operate at the level of the hosting provider's server -- we can't reliably oversee our users' hardware.
It seems to us that this interface needs to be automatic -- that the instant an outgoing email runs through the provider's server, it needs to duplicate to "our" backup. If it's done every day (or hour), the window exists for the volunteer to send an email and potentially delete it seconds later, irretrievably removing it from the server forever.
Can anyone advise a solution? We don't have the funds available to have Exchange for every user. We are happy to switch providers, or undertake any other practical and cost-effective solution that resolves our "instantaneous backup for all emails in and out" dilemma.
I'm happy to answer any questions, and thanks for taking the time to read this long setup.