Some details are:
1) after clicking on the send button, the icon to the right of the send button spins and spins without sending. After many minutes or longer, if she has the patience to stay on that page, a dialogue box will come up saying that the server cannot be used and to select another server. And I have seen this happen and 5 to 10 minutes is common in terms of wait time. Our ISP is cox here in AZ. My iMac does not have this problem and the email send time for me is 2 to 3 seconds or so.
2) On the MacBook Pro, I have deleted the smtp server in the account area and added it again. That sometimes worked but within a day the problem resumes. I have done this delete and set up again many times.
3) I have completely deleted the account and set it up again. I have done that several times.
4) I have repaired permissions, a couple of times.
5) I have zap pram based on Apple Cares suggestion.
6) After any of the above, I restarted the computer.
On another note, I have looked at the forum responses using different search criteria (MacBook mail problem, Slow email, can't send emails, etc) and I have seen many responses. Just a few moments ago I saw one about changing the DNS settings. I am not sure about this but this slow email problem seems to occur when she returns from a trip out east where she is probably using another server to send emails. Not sure if that is relevant or not.
What is kind of perplexing is that people are still having a problem.
Anyway, thanks for reading my post and responding.