Method One:
1, we click on the Mac Interface "Mail" and then go to find "preferences" under the "Advanced" option
2, then in the Advanced interface, we click on "Automatic detection of Account Settings" and "uncheck" Set up the first exit, and then open "Mail" and then check again
Method Two:
1, if the above method is not resolved, we check to see if the SMTP Setup problem
2, the recipient address can try to change a
If it is Sina Mail we can try IMAP , do not use POP3
"Note" VIP Mailbox open IMAP function, some mailboxes need to manually open.
1, good method four and method a bit like we click "Mail" to find preferences, find "advanced" click Options to enter
2, directly uncheck "Use mail drop send large attachment"
And then try again, is it okay to send an email?
Note: The mailbox of different mailboxes it will be different, especially now free mailbox has restrictions, or to open their own stmp can be used.