I’d always used one single email account and tried, wherever possible, to keep these accounts completely?separate?from one another. At work I now find myself using two IMAP accounts, one for work and one personal account. Setting the accounts up is a doddle but I noticed that messages I was sending from my work account where not getting store in my mailbox. After some fiddling I found that to have messages sent from one account stored in the sent mailbox for that account, you need to?explicitly?tell Mail.app what each of the server-side folders are to be used for. To specify this click on them and go to Mailbox >Use this mailbox for > Sent/Drafts/Trash. I just thought I’d share in case anyone else comes up against this problem.?