Trouvé sur le site d'une université américaine :
https://csguide.cs.princeton.edu/email/setup/imapconfig
(a faire sur les Réglages de l'iPhone)
Similarly to Mail.app, the defaults for the "Drafts," "Sent," and "Trash" folders on the iPhone may not align properly with the Zimbra IMAP server. Use the following instructions to finish the configuration of your IMAP account:
On the "Mail, Contacts, Calendars" settings page, select the IMAP account that you just added (eg "CS IMAP")
Scroll down and select "Advanced"
In the "Mailbox Behaviors" section, select "Sent Mailbox"
Scroll down and select "Sent" in the "On the Server" section
Touch "Advanced" in the upper-left corner of the screen
Select "Deleted Mailbox"
Scroll down and select "Trash" in the "On the Server" section
Touch "Advanced" in the upper-left corner of the screen
If desired, modify the "Removed" setting in a similar fashion to the above
Exit the "Settings" application