Hi Zhang,

I just discovered that the user experience when deleting mailboxes with default settings is not very nice.

When I remove mailboxes in iRedAdmin(-Pro) and don't choose a due date (i.e. keep 'Delete mailboxes in' untouched), 'delete_date' will be set to something like '2117-05-07', which seems similar to what happens with 'Keep forever'. This is not what I expected.

I would suggest that you change the dropdown to choose 'Keep forever' per default (not provide a 'Delete mailboxes in' selection at all).

Apart from that, I would strongly recommend to completely change the behaviour in case of 'Keep forever'. My suggestion would be to not set the 'delete_date' field at all in this case. With the current implementation, accidentally setting the system time wrong might lead to mailboxes being deleted which where supposed to be kept forever.

And besides, 100 years is *not* forever. Who knows, maybe some iRedMail systems will still run in 100 years from now and then people wonder where all the important mailboxes are gone, that where marked as 'delete but keep forever' in the past

==== Required information ====
- iRedMail version (check /etc/iredmail-release): 0.9.7 MARIADB edition.
- Linux/BSD distribution name and version: Debian 9 Stretch
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL/MariaDB
- Web server (Apache or Nginx): Apache
- Manage mail accounts with iRedAdmin-Pro? Yes
====