[Evolution] upgrading to 3.10.4

[Brian Russ <bjrus cooptel net>]

I have just installed Mint 17. Then I installed Evolution 3.10.4 and
used the backup/restore to carry on using my previous settings and past
messages etc. from Evo 2.28.3 on my earlier Mint installation.
The opening message about the change to maildir instead of mbox seemed
innocent but now my old account seems to be 'messed up'.
Is there an 'idiot level' explanation of what is going on ?  what should
I have done/need to do ?
Whether I can read any replies is not absolutely certain !