Would really appreciate some help if possible please
Mail has all of a sudden stopped sending mail in one of my accounts and after consulting with some of the helpfiles online and trying the suggested solutions - nothing works.
I upgraded my macbook air to mountain lion a week ago and since then have had no problems whatsoever until today. Literally mail stopped sending emails today from just one account whilst the mail application was open. I've not made any changes to the settings etc and the relevant mail account is working fine on my iphone.
I've tried changing the port to 587 as suggested by some people on here and that doesn't work. I've followed the apple support page http://support.apple.com/kb/TS3276?viewlocale=en_US&locale=en_US about troubleshooting mail problems and checking everything is configured correctly.
It's weird that it's been working fine since I upgraded and literally stopped working whilst I was in the mail application today - one minute I could send mail from the account, and then it stopped and the email started piling up in the outbox. I've checked the connection doctor and it gives me little green lights to every account. The error message I get is: "Cannot send message using the server mail.mydomain.com. Verify that you have addressed this message correctly. Check your SMTP server settings in Mail preferences and verify any advanced settings with your system administrator. Select a different outgoing mail server from the list below or click Try Later to leave the message in your Outbox until it can be sent."
I can see that a few people are having similar problems after upgrading but it's so strange that it seems to have worked fine since the upgrade then nothing apparent has changed and it's now not working.
If anyone has any ideas/suggestions or has experienced this problem also I would be really grateful for your help and advice.