(MAIL) Message could not be sent because your account does not have a preferred outgoing mail server

Please open the Mail preferences window and select the Composing tab. Make a selection from the menu labeled

Send new messages from:

If the selection is

Account of selected mailbox

and you get a warning that there is no preferred outgoing mail server, then select the Accounts tab and edit the account in question. Select a server from the menu

Account Information ▹ Outgoing Mail Server (SMTP)

Try Mail/Preferences/Accounts /Account Information. Select an account, then go to Outgoing Mail Server (SMTP). From the drop down menu select Edit SMPT server list. Then set up a server for each mail account so that is associated with the e-mail address. Then go to each account and set that server as the Outgoing Mail Server (SMPT). You can click Use only this server if desired.

Please sign out of iCloud in its preference pane and sign back in. No data will be removed from the servers.

If you use iCloud Keychain, when you sign back in to iCloud follow one of the procedures described in this support article to set it up on an additional device.