can no longer send mail after installing Yosemite

Having recently upgraded to Yosemite I find that my Mail App does not work properly anymore. I have all the same email accounts I previously used with Mavericks, however, Yosemite mail continuously does the following at various times (sometimes concurrently, and sometimes independently)

1. Pops up message saying my user name and password are incorrect. It does this on all my accounts, regardless of the server they are with (even iCloud at times).

2. Takes my accounts offline saying there is a problem with the server. The accounts are with different servers and Mail does not discriminate between them, thus the issue is with Yosemite, not the server.

3. Will receive mail but when I click to reply it just sits the mail in my outbox and refuses to send it.

4. Sometimes I have received mail but cannot click on it to open it.

5. Connection to mail server drops in and out randomly, telling me my settings are incorrect even though I do not change them. How can my settings be correct, and then incorrect, and then correct again etc without me changing them?

I contacted one of my internet providers to ensure my mail accounts were fine and the provider indicated my mail accounts are running fine and mail is ok with them. The issue only began after I installed Yosemite, so I know it is not a problem with my server or internet provider, but with Yosemite. It is an apple issue that Apple needs to fix. I am running a business and it becomes extremely frustrating when I cannot reply to a customer enquiry!!!

I have exactly the same problem and this comes from the beta version of Yosemite. Apple has not yet fixed.

Well, this is really weird. My service provider is Suddenlink. I have been having major problems trying to send after installing Yosemite. According to Suddenlink and Apple, I am supposed to use port 25 and not check SSL for outgoing mail.

After trying everything, I checked the SSL and it automatically changed the port number to 465.....and voila! I can now send email. I hope it will still be viable tomorrow!

I created new mail account with my data from the old account, but changing certain items such as SSL enabled (which supposedly my server provider does not support it), and the mail began operating. In other words, change some items in the configuration, although supposedly they are not logical, as the activation of SSL or any of the ports to make them work both server entry and exit points. This means that the mail is crazy and the problem persists. We will have to wait for Apple to fix incompatibility between Yosemite and mail

I have exactly the same problem .. i cannot send emails from any of my accounts except occasionally on Hotmail .. come on Apple fix the problem, it's too common now for it not to be a Yosemite fault !!

You are right; it is now too common a problem with Yosemite.

Do you think the Apple technicians read about these issues?

Ahji you would like to think so, but somehow I doubt it or surely they would have sorted something by now ! If it was a glitch with a small app that doesn't really matter then perhaps we could all understand, but a major problem with something as big as Mail is unacceptable .. this is something we all use daily. It has to be a Yosemite fault as I, like everyone else commenting, can send mail from iPhone and iPad but not from the Mac.

PLEASE Apple if you do read any of this, can we have a solution ... or at least acknowledgement that you know there is a problem that is being looked into.

I have there same problem. I cannot send from any accounts. BT (British telecom), Outlook or iCloud. My mail just sits in the outbox. NOTHING happens. I have deleted and reinstalled all my mail accounts. Buggered around with SSL settings. Tried everything suggested, even removing save application state from com. apple mail. Nothing works. It is definitely a Yosemite fault so come on Apple do something and stop passing the buck.

I have the same issue. This was a really big issue with Lion and not with Maverick, but it is back again. I can send and receive on my server so it is not my ISP who is the problem. I contacted my ISP to insure all settings were correct. I had no issue yesterday before installing latest software version. I can receive, but not send with Mac mail. NO SSL>use authentication, use password. All 4 of my accounts show SMTP off line, but in Mac mail all 4 accounts are on line. Been screwing around with this for 7 hours on and off.

Barb

Not sure if you remember, but this was a huge problem with Lion. There were like 15,000 posts. It's back again with Yosemite. People were changing ports to 587 from 25, deleting accounts and reestablishing, etc.

I am taking my MBA in to the Apple store on Friday morning. If the issue is not resolved by then, and they fix it, I will note it on here