Issues with Mail and SMTP and Gmail Accounts

Question

So this isn't a question....more like a solution that I had to figure out. 
We have multiple gmail accounts in our family and after upgrading to OSC Yosemite our gmail accounts wen't haywire.  My wife was sending emails that eventually were sent from my gmail account (mass neighborhood emails at that.....and all replies came to me instead of her).  I spent about 2 hours investigating and put together several different threads that finally fixed out problem.  The root of the issue is that you can share the same Incoming Mail Server for all of your gmail accounts and your mail will go to the accounts that it is supposed to go to, but you have to have individual Outgoing Mail Servers for each of your accounts otherwise all outgoing mail will come from one account only.  I don't know why this happened, it is a pain in the butt, but here's how I fixed it with 3 gmail accounts running through 1 mac.    
1st - you need to remove all of your gmail accounts from mail via Internet Accounts in Settings. Just highlight the account and hit the minus sign at the bottom.  You won't lose anything if you have your gmail settings set to default which backs everything up to Google's servers....it will all load back to you mac and it will all be available online at gmail.com
2nd - you need to add back all of your accounts one at a time (and follow all of the following steps for each account before adding another).  Select the plus sign and choose Google (for gmail accounts only). 
3rd - Give your gmail account a recognizable name in the "Name" field (if you have multiple Gmail accounts to add, you will want to distinguish between them).
4th - type in your username ([email protected]) and password.  Make sure to add the suffix @gmail.com. 
5th - Check the boxes that you want to add to your mac (mail, contacts, calendars, messages, notes). 
6th - Click the "Details" button to ensure that you have an adequate description (see # 3 above) if you are going to have multiple gmail accounts to add. 
7th - Open the Mail app.
8th - From Mail Preferences/Account Information Tab - make sure that you account is Enabled (check box next to "Enable Account", make sure that you have an adequate description name, email address is correct, Incoming mail server is imap.gmail.com, Username is your normal gmail login username (absent any suffix like .gmail.com), password is your gmail password. 
9th - Then, from Preferences click on the Advanced tab and....Uncheck "Automatically detect and maintain account settings".
10th - Then, go back to Account Information Tab and.....from the Outgoing Mail Server (SMTP) dropdown box, select Edit SMTP List....
11th -  You need to create an individual SMTP Server Account for each gmail account that you plan to add.
12th - To do this click the plus button.  Server Name should always be smtp.gmail.com.  Type in your own Description (I recommend naming it after the gmail account that you plan to attach it to). 
13th - TLS Certificate should be "None"
14th - Click the Advanced Tab - From here, uncheck the box for "Automatically detect and maintain account settings".  Then make sure Port is 587 (default is 25 for some ungodly reason).  Check the box for "Use SSL".
15th - Set authentication to "Password".  User name MUST contain a suffice (i.e [email protected]).  Password is your normal gmail password. 
16th - Click OK. 
17th - Now your back at Preferences/Account Information - Link your account to the SMTP server that you just created by using the dropdown box next to Outgoing Mail Server (SMTP). 
18th - Save all changes and close out of Mail App. 
19th - Restart Mail and recheck steps 8-15....for some reason my passwords kept getting erased, but they eventually saved and took. 
20th - Add another gmail account by following these steps and then recheck all along the way for passwords, suffixes, everything.  You will want to make sure that your accounts are all properly linked to their respective Outgoing Mail Servers (hence the distinct naming descriptions).   
21st - Once you have added multiple accounts send email between them to make sure that they are being sent from and received to the correct accounts. 

Answer 1

Wow! Oh my goodness Patrick, thank you so much man. That's a ton of informatiion to take the time to write out step by step and share with strangers.  I really, really am grateful to you.  I've been dealing with this for a month, half the month I kept changing my passwords and kept assuming I was making some mistake.  It used to work fine.  About a week ago I started looking for a solution and couldn't find one that worked. 
You have changed that sir!  I'm good to go, stress level will lower when I am on my Mac, and I'm so glad to not have all these messages popping back up that I was done with! 
Muchos Gracias Amigo!  Owe you one...