Mac desktop. trying to send email, message: SMTP failed? No new changes to computer.

Question

Mac desktop, trying to send email, message say-SMTP failed.  No new changes have been made to this Mac.

Answer 1

iOS does not run on Macs.
Not knowing your operating system or Mail program we can't give you much detailed help.   Go to Apple menu -> About This Mac to find your Mac OS or Mac OS X version.  If it is an X version, please post in the right forum:
http://discussions.apple.com/docs/DOC-2463
SMTP servers are of two types.   Those associated with the internet provider giving you the internet access.  I.e. if you have Verizon FiOS for Fiberoptic internet your SMTP server would be something based on verizon.net.   And those associated with separate web/e-mail host providers if you have a personal website or e-mail provider you chose from before you switched to the current internet access provider.   If the latter, it is possible the internet access provider, in order to prevent being implicated from being the source of spam has decided to enforce port or password authentication on the SMTP server to ensure you aren't a spam bot.  In that event, you'll probably have to check with them if it is better to use port 2626, 2662, or 587, and password authentication.  You may have to check with both e-mail provider and internet access provider.    Usually when you have separate providers doing both, your e-mail address is your username, and password on password authentication is same as checking your e-mail.