|Springmail mailboxes are generally not large enough to utilize IMAP, because the mail always stays on the server, the mailbox could easily fill up within a year or two of use.|
If you are using Outlook and are downloading your mail via a POP3 setup, then that will do the housekeeping to keep your mailbox from filling up. If you also want to use a smartphone to access your mail, be sure to set Outlook to leave a copy on the server for a number of days (14 or 30 is common).
Then you can setup your phone to "sync" with the mailserver by using IMAP. Your phone will then mirror the mail that is left in your mailbox (the last 14 or 30 days of mail).
SETTINGS FOR IMAP:
You will need to manually type these into your phone settings. Auto-configure will not work.
Port #: 993
Username: (your full email address including the @domain name)
Password: (your password)
Authentication: Password (you may not need this setting)
Port #: 465
Username: (full email address)
Password: (your password) (even if your phone says "optional", it is not. It is required)
Authentication: Password or Required (you may not need this setting)