Cannot send message using the server smtp.

I have been having the same problem for close to a month. Perhaps this will help to clear things up:

Receive AND SEND work fine on my two other apple machines which use mail with the EXACT same settings on the EXACT same (as well as other) networks.

The settings are also exactly the same on two android devices with no problem.

I have edited as well as deleted and re-entered the SMTP server information.

In the past I would occaisionally be unable to send from my other apple laptop, but either attempting to resend, or just deleting and recomposing an email was enough to get around it (I assumed it was an outbox glitch.) Unfortunately, this has been consistent with the apple machine in question for nearly a month.

This machine has been able to send emails through the mail.app without issue for the past 8 months from connections all over the world, with and without VPNs in place.

Receiving has never been a problem.

I just spent a few hours on this problem and finally got it fixed. The frustrating thing I learned is that identical settings don't necessarily work on different computers. I use three different email addresses. One is an ATT address and it works great receiving and sending on my ATT server address. The other two use personal domain names. On my other computers I am able to send mail from those other two addresses. On my new Macbook Pro I could not. I finally paid for advanced tech support and he was able to fix it by using outgoing mail server addresses that my personal domain is based on. So now I use different outgoing servers for the different email addresses. Why the ATT outgoing server still works on the older computers for sending mail for all three addresses is a mystery, but it might be tied to IP addresses -- suddenly you have unrecognized domain names from a new IP address and the server doesn't like them anymore. That's just a guess.

Hi all, I had this problem for about a week but seem to have fixed it following some of the advice in this thread.

I don't know why I used this account for over a year in Mac Mail no problem then suddenly starting getting the error message 'cannot send message using the server smtp. Pretty frustrating after a couple of days, lucky my other accounts still worked. So what I had to do:

Mail tab dropdown > preferences

selected the problem email account

> outgoing mail server (SMTP) dropdown

> selected 'edit SMTP server' at bottom of list

> I then changed server name, originally it was 'smtp.mywebsite.org' I changed to 'mywebsite.org' and saved

That worked for me

Cheers