Q: os x update 10.10.4; mail won't send 6/30/15

plain login dosn't work anymore with mail and SMTP!

Nobody know why, and APPLE ignores the problem?

I have same issue with outlook unable to send email comes up with msg Connection to the server failed or was dropped error code -3253 have deleted outlook re loaded as well as set up accts a number of times without any sucess

HI I had the same problem.  Could not fix it on my own.  Had to call the university's Helpdesk.  Took the guy about an hour and a half, but he figured out that if the email server (like the university's) is a gmail account, you can't go thru the university's server.  You set it up on the Mac as a google account using the user name and password for the university account

After days of frustration and deleting and recreating mail accounts I finally got my outbound mail to send. It was an easy fix once I tried it.

I went to "Mail" "Preferances" "Account Information" and removed the checkmark from "Enable this account". I did this for all of my accounts.

I closed the window, saved the settings, closed Mail, then did a Restart

Then went to "Mail" "Preferances" "Account Information" and checked "Enable this account" for one account

Then I closed the Window and saved the setting

I created a test mail and sent it. Nothing happened for a minute or two then it asked for my email password. Entered it and swoosh went my mail....

Then I just enabled my other accounts and all is fine.

Fantastic--mail now sends out albeit a little slow.  Thanks for an easy fix.

I Think that may be because of the new feature Google started a week or two ago (mine does the same thing). It gives you a few seconds to change your mind about sending an email.  I'm guessing that if in those seconds of lag time, you regretted pushing send, that you could go into your outbox and delete the email

I have the same sort of problem as most on here... after installing 10.11, I could receive but no longer send mail from any of my three POP accounts, which I have through GoDaddy's "smtpout.secureserver.net" server. As soon as I set the perimeters and did a save, the settings were lost. Basically Mail was changing the name of the outgoing server to "pop.secureserver.net" (the name of the incoming server), unchecking my "SSL" check, and changing the port from 465 to 80. My work-around is easy: In Mail, open "Preferences", then "Accounts", and set the correct name and settings for the outgoing server. Click back on Mail so the "Accounts" box disappears and Mail will hold on to those settings as long as Mail is open. But as soon as you close out of Mail and/or shut down your computer, you'll have to once again enter the correct name of the outgoing server and the SSL and port settings. Hey, it works - at least for me - until Apple gets around to fixing this bug in upcoming releases.

Thanks! I did the following (may help user whom Linc's advice didn't help):

In Mail Preferences/Accounts/Advanced, uncheck "Automatically detect and maintain account settings"

Then restart computer.

When I did this, a test email in the Outbox / iCloud account sent immediately on restarting. I then re-ticked the 'automatically detect' boxes for both Gmail and iCloud accounts and sent a test Gmail, which also sent immediately. Previously gmail had seized for maybe 6 months and iCloud for a month or so and I'd given up trying to send emails from this laptop (email has always worked fine on desktop with exactly the same OS, 10.10.4). Seems problem may be device-specific.

So the 10.10.5 update did not fix my problem.

I still have to press SHIFT when I start Mail, and then it runs OK.

Anyone have any suggestions?

Interesting about "shift" and restart Mail... hadn't heard of that method. I tried it and while it did maintain the check on SSL and the correct port setting, the name of my outgoing server had changed from "smt..." to "pop...".

I've been experiencing this problem on and off ever since my upgrade to Yosemite, and tried most of the suggestions with no lasting success. However, I've noticed something interesting - the problem seems to occur much more often with frequently used addresses.

So, I created two emails, one to an address that I've mailed to quite frequently and one to an address I never email - my old business account. In the same "send" the frequent address failed and the never-used address was sent just fine.

I'm not technical enough to know what it might mean, but thought it might give someone else a hint to solving this PITA problem.

Thanks Linc.  I was so frustrated.  I had to shut down mail and re open it every time I wanted to send something.  That did the trick.  Much thanks for posting.   Eileen