Why do my SMTP/IMAP/POP servers keep going offline in OS X Yosemite Mail app?

This suggestion seems to work (at least for some time). Though there appears to be no need to check the "allow insecure authentication".

Few things that help me manage the Apple mail problems with IMAP clients that have appeared since my Yosemite upgrade:

* Using the app-specific passwords (if you have that set up, example for Gmail on Mac) to set up the Gmail account. Use the generated password instead of the one you use for login to Gmail.

* The default setting and the auto detect functionality should allow the mail to start flowing, both in and out.

* If the auto detect of settings does not work, checking the smtp outbound port info. As this post suggest, turn of auto detect and use the specified port. E.g. Gmail uses Port 465 with SSL (also 25 as another option) and Port 587 with TLS.

Agree that Mail has become a bit flaky after the Yosemite upgrade.

I could swear that I have made this change a half dozen times in trying to solve this issue -- which seems to come up with every upgrade! But this time it seems to be working -- based on one data point. Thanks!

I have gone through every post and tried every recommendation...changing the outgoing port to 465 worked! I was able to keep everything else the same, but did have to enter my password again after changing the port number. Thank you!!

I solved my Mail issues by not using it anymore until Apple fixes it. I have downloaded Thunderbird and no longer have a problem sending or receiving emails. I don't like the layout as much as Mac Mail, but I am willing to live with it because it works.

I have similar headaches on my company POP account since "Side-grading" to Yosemite on my laptop.

I have unchecked "Automatically detect and maintain account settings", but my account still keeps going offline.

Strangely - sometimes I still get mail for brief periods on the account when the "Offline" badge is showing.

It's not a password issue - connection doctor does not say password is rejected. It says account settings are wrong.

My Mail on my 2013 iMac, which is running Mavericks, is running fine with the same settings.

At this point, the Yosemite Mail app is unusable, which means the OS is unusable.

465 is the correct SMTP port for SSL secure email. A further bug I have found however is that Apple Mail keeps changing the port setting to 25. I set it to 465 and all is well for a while then for no obvious reason, the outgoing server goes offline and when I check, the port is changed to 25. As soon as I put it back to 465 it is OK. I would like to know how this change is triggered

for what it is worth my gmail account is permanently offline showing incorrect password or user name. I have tried every single one of the suggestions and not one works. This is also the case with my orange.net account. I have updated to Yosemite and all worked well until about two days ago.Works ok on my iPhone5s but not on my iMac or laptop.

I love all things apple but this is starting to really annoy me.

Tried to contact apple but they want to charge and gmail help is useless.

Maybe I can help -

We went through the mail **** when we first switched to Yosemite and are now up and running again reliably.

Your problem may be different, but it's worth a try.

Our solution was:

Turn of the auto-settings features in Mail.

Contact service provider and return settings to their recommended settings.

Check with service provider that your IP is not locked out.

For those insterested, here's how the whole mess happened in the first place:

1. Mail's two auto-settings features caused an initial failure to connect to our mail server.

2. We then went through a number attempts to troubleshoot and finally our service provider noted that the auto-settings features in Mail had set the wrong settings.

3. We turned off both auto-setting features and returned the settings to the correct ones.

4. But the server had interpreted our repeated failed attempts to log on to our server as a malicious attack and had locked out our IP address.

5. Once we had our provider unlock our IP and returned our settings to what they were before Mail had fudged them, everything was ok again.

We had done diagnostics with a Level 2 Apple tech and he was unable to solve the issue, and suggested our provider needed a software update, and that the problem was not caused by Mail. As you can see, we found later that this was not the case - the problem was triggered by Mail's failure to set settings correctly and then compounded by the lockout by the server.

Please click the link below to resolve this problem. Yahoo mail in Apple mail requires an app specific password in order to function normally.

Kind regards

Anthony

https://help.yahoo.com/kb/yahoo-account/generate-separate-quotapp-passwordquot-s ln15241.html

I struggled with the same problem using OS X 10.9.5. It has happened twice now for no apparent reason. My outgoing SMTP server continued to stay "offline". I could receive mail, but not sent mail out. Here's the solution that worked for me (the others posted did not).

Go to the account in Mail Preferences

Go to the "Account Information" tab

At the bottom of that screen you will see "Outgoing Mail Server (SMTP):"

Click on the drop down menu and at the bottom of the list you will see "Edit SMTP Server List", click that

On the screen that comes up is a checkbox for "Use Secure Layer (SSL)"

This box was checked, but when I unchecked it, my outgoing mail server went online and I could once again send mail out.

I have no idea how this box got checked by itself, but this was the same root cause the last time I had the problem.

The other setting on this screen were as follows (I did not need to change these, by the way)

"Use default ports (25, 465, 587)" was selected

For "Authentication", Password was selected

For "User Name" my primary ISP email address was present

For "Password" the password for my primary ISP email address was present

Hope this helps.

I believe the problem is SSL. If the server your mail is hosted doesn't have an SSL certificate then Apple Mail won't work for you anymore. I have a client that has a number of mailboxes on his Mac. Only one of them is hosted by me and this is the only one not working.

If you try ticking the SSL box it might work for a while but then it will constantly ask you to verify the certificate and won't send.

I'm losing faith in Apple.

I now have the choice of installing an SSL on my server and having to tell all my clients to tick the SSL box, or tell the small number of Apple Mail users that they need to switch to Thunderbird.

SOLVED. I signed on mz google account on myaccount.google.com and turn on the "acces for less secure apps" to -allow- and inmediatelz solved the problem.

Hope this solves zours too.

This actually worked for me also, thanks for the suggestion. I have been waging war on this problem for ages. It is just my wife's MacBook 13 Aluminium Late08 which has the problem, my MacPro talks to the SMTP server okay. Apple have really lost the plot so far as design is concerned; it is a complete mess. Especially if you factor in setting up the accounts on the iPhones and iPads as well. Our ISP's smtp server requires that we have password authentication, no SSL and insecure authorisation enabled. On my computer, when setting up for the SMTP server I can do this without any trouble. On my wife's machine (both have OS X 10.10) in the same SMTP set up dialogue it is identical except there is no "Allow insecure authentication" tick box and it is only in that detail that our set ups differ but it is this which means I can send mails and she cannot. We both have the aia box ticked in the IMAP part of the Advanced tab for each account. It is bizarre and frustrating. So I hope the random change to MD5 etc. provides a lasting solution. I am sceptical, in the same way I am about mechanics who lift the bonnet and just wiggle things but maybe they get lucky too. I fully expect it all to break next time there is an update but, for now, we can work again!

That worked for me. Thank you!