Q: Mail not working with El Capitan

This worked for me but once I uncheck auto I needed to quit mail and come back in. Thanks

Thank you for your suggestion to turn off autodetect! My email is coming in again!

1) Open mail

2) Select preferences

3) Click on the account icon

4) Select advanced tab

5) Uncheck the automatically detect and maintain account  settings box

This should fix it.

My POP email stopped working in the last 24-36 hours. Even after upgrading to El Capitan, it was working fine for about 2 weeks. I cannot think of any reason as to why it should stop working. Mail Connection Doctor says that the password might be incorrect. That is not the case. I setup the POP account using the same credentials on a PC (using Outlook) and it is working fine. Here is my error/log. I have removed my name and domain name and replaced it with generic "domain.com".

WROTE Nov 06 18:19:35.981 [kCFStreamSocketSecurityLevelTLSv1_0] -- host:pop.secureserver.net -- port:995 -- socket:0x7fa91df7de70 -- thread:0x7fa921392dd0

CAPA

READ Nov 06 18:19:36.055 [kCFStreamSocketSecurityLevelTLSv1_0] -- host:pop.secureserver.net -- port:995 -- socket:0x7fa91df7de70 -- thread:0x7fa921392dd0

-ERR authorization first

WROTE Nov 06 18:19:36.055 [kCFStreamSocketSecurityLevelTLSv1_0] -- host:pop.secureserver.net -- port:995 -- socket:0x7fa91df7de70 -- thread:0x7fa921392dd0

APOP user@domain.com fc21a7dd3c25e8a98681cc7cf9407b29

READ Nov 06 18:19:36.182 [kCFStreamSocketSecurityLevelTLSv1_0] -- host:pop.secureserver.net -- port:995 -- socket:0x7fa91df7de70 -- thread:0x7fa921392dd0

-ERR authorization failed  Check your server settings.

WROTE Nov 06 18:19:36.183 [kCFStreamSocketSecurityLevelTLSv1_0] -- host:pop.secureserver.net -- port:995 -- socket:0x7fa91df7de70 -- thread:0x7fa921392dd0

USER user@domain.com

Spent a few hours reading thru everyone's posts, after upgrading to El Capitan yesterday and my POP mail stopped working.

Apparently on the upgraded Advanced tab (Preferences --> Accounts --> "selected account" --> Advanced), there is a new little checkbox that says "Allow insecure authentication". I never noticed this before, so I assume it's new.
When I unchecked this box, the System Error triangles all went away and my inbox flooded with all the emails that had been sitting on the server waiting since my last download. I don't know if this will work for everyone, but it did resolve the issues I was having with my POP accounts not being able to connect to the server.

This might work, but probably not a good long term solution - unchecking that means disabling SSL.  Probably don't want to be sending your login info (and all of your mails) in cleartext over the public network. 

Quitting mail, turn wifi off then back on, re-open mail has worked for about a week here.  Fingers crossed it will stay that way until they can push a fix...

SSL is checked (Port 995) but the "Allow insecure authentication" is also checked -- so far so good. Also, Authentication type is "Password", so terribly secure in the place, but at least there are no more error messages and I am getting all my emails.

@erinlima - A BIG THANK YOU for pointing this out. YES, YES it did work for me. I don't care at this point, if my credentials are going over a public network without SSL, but I got my emails. It is like getting eyesight back again.

Hrmm, it could well be that you *are* still talking SSL?  I'm not sure what "Allow insecure authentication" means - I've got it unchecked and it is working here (for now).  If anyone knows exactly what that checkbox means please do tell!  Does it maybe fall back to non-SSL if the TLS negotiation fails?  Googled a bit without much success. 

JC93430's idea above worked for me.  I still have all the authentication working, but the email is working now.  Just unchecking the automatic detect got everything working immediately.

None of my pop accounts were working (exchange was) and when running connection doctor it said that the username or password was wrong, even though they were right and worked on all my iOS devices fine.  Unchecking that box fixed it all.

Seemed to work when I unchecked "automatically detect and maintain account settings", but as soon I rechecked it, it went back to the previous state of no incoming messages..  I guess i'll leave it unchecked for now

Has anyone a solution to my issue?

On the advice of Apple support, I deleted the POP mail account and am now unable to recreate the Mailbox.

Each time I put in the correct details, I get an 'Unable to verify account or password' error message.

So far all the solutions that appear to work for others are about unticking the ticked boxes in mail parameters but what about those who are unable to create a new mailbox?

Apple? Anyone?

Spotlight refer to JC93430 on 1/6/15.

Thank you for your reply.

I have attempted to do a search on the information you give but am unable to find a posting that dates back that far attributed to JC93430.

Are you able to paste a link to the article?

Thanks.

The info in this post worked for me.  Re: Mail not working with El Capitan

1) Open mail

2) Select preferences

3) Click on the account icon

4) Select advanced tab

5) Uncheck the automatically detect and maintain account  settings box

This should fix it.