"sorry guys. I am so frustrated with this issue. My Macs have worked flawlessly for the past year and out of nowhere it just started up.
Gmail - using gmail outgoing servers
Internet service provided by AT&T - tried using the ATT smtp and nothing"
I'm coming into this thread a little late, but I'll try to help. This is a long post, please save it and/or print it out.
Pat park -- you said you're with ATT, so am I. In fact, after using ATT dsl for a decade, I just switched over to ATT Uverse about 10 days ago, and that's when my own "can't send email" problems began.
You aren't alone, MANY Mac users have the same problems, particularly with ATT Uverse.
ATT blocks "port 25" by default. This is the normal "outgoing" port for email (the "smtp" parameter you enter).
There are other "out" ports (may be port 587?), some folks experience success using them, but others don't. I tried -all kinds- of re-configurations to try to get Mail.app to work with my new Uverse setup, and couldn't. I suspect that the reason I couldn't "get through" is because my email address is tied to a "legacy server" ("xxx@snet.net"), instead of being simply "xxx@att.net".
Interestingly, I found that if I used Thunderbird to send email (instead of Mail.app), the outgoing email would send without problems, even though all the account parameters were the same.
I've come to the conclusion (based on my own hunches, I'm not a software expert) that there is -something- in Mail.app that can't "let go of" port 25, even when you specify a different outbound port for email. Or, it may be in the way Mail.app combined with the Keychain handle the [host] server's password query. Thus, even though you've configured it to send to a different smtp port, Mail.app is still trying to "touch" port 25, and because ATT blocks port 25, the whole process of sending mail grinds to a halt.
There is a very easy way to cure this problem:
Contact ATT and have them TAKE THE BLOCK OFF port 25 for your account.
Once I did that, my email problems with ATT -DISAPPEARED-, and things are back to normal.
HOWEVER -- it can be VERY difficult to contact ATT and get this resolved. You have to know the right number to call, the right things to say. Keep reading.
By phone, the number you want to call is 866-757-9808. This is "tier 2" tech support. Ignore the "press 1 for xxx" at first, then wait. You should hear something to the effect "if you are tier 1 tech, press 1". THIS is what you want to do, so press 1. You should next reach a level-2 tech.
Give him/her your account info. Then explain that you are a Mac user, that you can't send outgoing mail, that you have tried alternate ports and that they don't work. Specifically request that port 25 be "un-blocked" for your account. It has been recommended that the language to use is "I would like SMTP outbound on port 25 unblocked".
The tech person is probably going to resist doing this. You may be told something to the effect, "I can do that, but it might be questioned if I did". Then you might be told that you need to be connected to something called "Connect Tech". DO NOT LET THEM DO THIS, the Connect Tech is a scheme to get you to subscribe to a $15 per month service contract. YOU DO NOT NEED THAT. All you need is to have port 25 un-blocked.
I didn't know this at first, so I let them forward me over. When I talked to the ConnectTech and found they wanted to sell me something, I ended the conversation immediately.
It's possible that (knowing more than I did the first time) you -may- succeed in getting the Tier 2 tech to take the block off. Be aware that I've heard of them charging a one-time $29 fee for this. I didn't end up paying it, perhaps others have, but if they had told me I would have to pay that, I would have paid, for ultimately removing the block was the only way my email would work.
I have an email address (that I haven't used) that -might- help you:
uversecare@att.com
In the subject line put the following: [Trouble]
(again, I haven't used this, and if you can't get outbound email to work, it won't help!)
What finally worked for me:
I managed to contact an ATT tech support person (probably in S. Asia) using their "live chat" feature, which you can find at this URL:
https://pattta.att.motive.com/netagent/questionnaire_uverse.aspx
Again, I went over the problem, explained I was a Mac user, emphasized that I was using a legacy (3rd-party?) server instead of "att.net", and requested that port 25 be un-blocked for my account.
The tech person said they would take the block off, did so, and verified that it was off.
Since that time, my Uverse outbound email now sends immediately without problems.
Perhaps this will work for you, and for anyone else reading this who uses ATT Uverse.
(((