Q: Not been receiving emails for 2/3 days - this is only affecting 1 user on this iMac

Hello Goudy Bold,

After reviewing your post, it sounds like the mail account is working with other devices. So it sends emails but not receive them on this one iMac user? I would recommend that you read these articles, they may be helpful in troubleshooting your issue.

It sounds like you have already seen this article. 

If you can’t send or receive email on your Mac - Apple Support

Since there does not seem to be a connection issue there may be an issue with the account in Mail. One thing that can be done is remove and readd the account. 

Mail (Yosemite): Set up Mail with your email accounts

Remove an account

When you remove an email account from Mail, the account’s messages are deleted and no longer available on your Mac. Copies of messages remain on the account’s mail server and are still available (from webmail, for example).

Important:   If you’re unsure whether messages you want to keep are still on the mail server, move or copy them into a mailbox stored on your Mac (the mailbox appears in the On my Mac section in the Mail sidebar) before you delete the account in Mail.

 

1. Choose Mail > Preferences, then click Accounts.

2. Select an account, then click Remove .

Thanks for using Apple Support Communities.

Have a nice day,

Mario