Yosemite Mail 10.10.2 - SSL port, Certificate not trusted, email can't be seen

Question

Hi All,
Thanks in advance for your help.
I have just upgraded  (quite regrettably) to Yosemite 10.10.2 with a clean install (Time machine... that's a whole new bag of tricks hasn't worked can't even reinstall mail via TimeMachine RESTORE.. very helpful apple)
Mail – The simplest of software, is causing no end of problems:
PROBLEMS:
1) When mail opens, it kept saying "Certificate for this server is invalid"
2) The 2 email accounts I have, keep going offline? NEVER had this on any of the macs i've had set up before ran 10.6.8 for ages not a blip?
3) And another glorious trick, even if the email accounts aren't showing any exclamation marks (about being off line)
I select any mail box AND out of nowhere, no emails show in the mail boxes, where only 10 seconds ago they were all there?
4) REPLY ALL just a few moments ago DIDN'T work or reply to all
NOW, it either replies to ALL including me (the original sender) OR it'll place the original sender email address in TO and all others in CC? when all emails were in the TO field?
Just to be clear: I have set up 2 email accounts as IMAP on the mac (Say email X and email Y), and have tested by sending an email FROM email X TO email Y and a hotmail account, just to have more than 1 email address in the to field to see what happens with the REPLY ALL. It doesn't work suffice to say
SOLUTIONS TRIED BUT NOT WORKED SO FAR
I have scoured the forums and tried a few suggested things
1) I have 2 email accounts, both of which I'm setting up as IMPA,  my ISP Tech support for email host has said "Set the SSL port to 587"
– Tried doing that in 2 places
a) Mail > Accounts > (select email account) > Advanced  There under PORT stated 587
b)  Mail > Preferences > Accounts (select account) > Advanced > PORT And here it is NOT the stated 587, it's (currently) 143?
(I've tried changing this to 587) and this doesn't solve the problem(s)
2) I tried UNTICKING "automatically detect and maintain account settings". but this didn't solve anything, and the whole certificate error and Mail going offline started up pretty much instantly
3) Tried ticking the "Allow Insecure authentication" - Again, no solution?
4) I did have my gmail account set up, but took that out of the equation as that wasn't helping, and with that I couldn't hit REPLY ALL and it show up in the TO field????
I appreciate this is a lot of information on the screen, but i've tried to be as through as I can, and seriously I CANNOT believe Apple have managed to mess up a corner stone app that should Just work?
Thanks agin for any help or pointers.
Mypetshadow

Answer 1

CAVEAT:
1)I'm not technically qualified, but thought i should share the info I have found that works for me after having a tech guy from the ISP sort out the settings to get my main running:
2) This has been working for all of 2 hours... lets hope it stays that way.
3) My emails are set up as IMAP accounts.
So....
After speaking / emailing with my ISP and after 4 days of what seems like ****... (Seriously, thanks Apple "it just works.... like a hole in the head") I have a few solutions that are working for me and thought I would post them up for people who maybe having the same difficulty...
SSL PORTS AND CERTIFICATES ISSUE
1) Once you "CREATE' an email account, you have to adjust the settings manually (No surprise there)
• There are some people saying you have to UNTICK the "Automatically detect and maintain my account settings"
• (I'm NOT a techie kinda guy), BUT in my case I LEFT THIS CHECKED (on advise from the ISP tech guy), and for me it is working. The tech guy from my ISP said something on the lines of  "If the PORT is 993 then SSL has to be checked, If it's port 143 the SSL IS UNCHECKED"
Again, i'm not a techie, but this may be of relevance to you.
Screen grab of the main IMAP settings page
2) EDITING the SMTP settings
• MAIL > PREFERENCES > ACCOUNTS > select your newly created account > ACCOUNT INFORMATION TAB
– From the OUTGOING MAIN SERVER Dropdown list, Select EDIT SMTP SERVER LIST and change your port to 465 (note: Originally port was 587... read below)
Here, SSL WAS CHECKED, as was "Automatically detect and maintain account settings".
REPLY ALL MOVES EMAILS INTO THE CC FIELD
• Originally the port was set at 587 BUT I noticed a glitch; when I hit reply all, this would put all email addresses that were in the TO field into the CC field? (excluding the original sender...) Not helpful.
• I noticed  (in an earlier mess up and moving around of ports etc) that when the port was changed to 465 (another port that the ISP tech guys said was an option) my email started behaving as expected... emails in the TO field stay in the TO field, as expected. and not placed in the CC field
Screen grab of the SMTP edit page:
Right, that's my non-techie tuppence and hope that it is of some help, and if not specifically all you need, it might give a few clues.
Cheers