Scheduled emails don't work

Hi, as per the subject, I have problems with sending scheduled emails, before they worked, now I don’t know why they don’t work.
I created a user in outbound who can send outgoing emails (the sending test works), I associated the email scheduling to this, but every time the scheduling time arrives, this error appears:

Inbound Email Connection is not valid resource for getting New Message Ids.
Job 4ef58564-a63e-987a-bf22-650074ad6787 (Run Nightly Process Bounced Campaign Emails) failed in CRON run

repeated for each minute several times.
The current version of suite is:

Version 7.12.12
Sugar Version 6.5.25 (Version 344)

the scheduling worked in a previous version.
Please, can you tell me how to solve it? Thank you

Would you upgrade your 7.12.12 to current supported version 7.14.3 (upgrade guide), retry your Scheduled Email Campaign, and report back your results here.