very possible, the issue is as you noted..... the password exists (at times no, issues) at other times issues (requring its entry) and a logical sequence of events - boot - Internet connection - Servers - cloud - mail start up
- authentication - password location (cloud/keychain) are not being completed successfully requiring manual intervention.
hense the term communications or software interface link, I have spoken with apple in the past on this subject
(deleting/re-adding email accounts) and as going as far as building a secondary account on my mac to test if it is a user email account issue to test out the sigin (userid/password combination - authentications) to the mail servers and it turns out to be a non issue later in the day.
the only thing I have done, is make sure my macs are upto date on software,
have built my accounts using the cloud on start up (adding an account the first time as a new admin)
instead of skipping that step and adding the cloud connectivity or sign on after I have set up my desktop
preferences/safari/mail etc.
since following this path all has been good and yes this speculation is for the engineers/archietects and experts