[Dovecot] Disallow POP3 from deleting messages

[DormitionSkete@hotmail.com]

On Mar 20, 2013, at 6:43 AM, Timo Sirainen wrote:

> On Wed, 2013-03-20 at 06:39 -0600, DormitionSkete at hotmail.com wrote:
>> I'd like to use Dovecot as our IMAP server when our users are within our LAN, but I'd also like to give them the ability to access their emails via POP3 when they are outside the LAN.  I know most POP3 clients will give their users the option of not deleting the messages from the server after they are downloaded, but is there any way to restrict them from being able to do so at the server level?
>> 
>> In other words, I want to disallow the server from accepting the DELE command from POP3 clients.
>> 
>> Is that possible?
> 
> You could create a (global) ACL to not allow user to delete own mails.
> But some clients will probably keep redownloading the same mails over
> and over again then.
> 

Thank you for the speedy reply!

Is there any chance you might consider implementing this as an option sometime?  I assume the POP3 delivery code is separate from the IMAP code.  You wouldn't necessarily need to return an error code to the email client.  Most clients probably wouldn't know how to interpret it anyway.  Just quietly ignore the DELE command.  

Or would that leave us in the same position, where some clients may keep redownloading the same messages?

Also, how would I create a global ACL like you said, so I could test how our clients would react?  Everybody here uses Macs, iPads or iPhones. We would not necessarily have to support a wide variety of clients.

We're using sendmail.  I assume this is done in sendmail, not Dovecot?  Or should I go to the sendmail group for that, if I can't find anything on the net about it with Google?