[MlMt] Issues with Outlook365 SMTP

[Marco Qualizza]

Hello all,

I was hesitant to send this because I can't be the only person using 
MailMate for Exchange.  But, maybe someone's seen the issue and can 
figure out what's going on.

For about 2 weeks now, I have been able to send email via Outlook 365.  
IMAP is working perfectly fine for the same account.

In the activity windows, I get

```
13:16:19 C: EHLO [192.150.23.129]
13:16:19 S: 250-YT1PR01CA0102.outlook.office365.com Hello 
[192.0.137.247]
13:16:19 S: 250-SIZE 157286400
13:16:19 S: 250-PIPELINING
13:16:19 S: 250-DSN
13:16:19 S: 250-ENHANCEDSTATUSCODES
13:16:19 S: 250-AUTH LOGIN XOAUTH2
13:16:19 S: 250-8BITMIME
13:16:19 S: 250-BINARYMIME
13:16:19 S: 250-CHUNKING
13:16:19 S: 250 SMTPUTF8
13:16:19 Retrieving password (keychain or user request)
13:16:19 C: AUTH XOAUTH2 ••••••••••
13:16:25 S: 535 5.7.3 Authentication unsuccessful 
[YT1PR01CA0102.CANPRD01.PROD.OUTLOOK.COM]
13:16:25 Error: Unexpected return code 535 (expected 235):
“5.7.3 Authentication unsuccessful 
[YT1PR01CA0102.CANPRD01.PROD.OUTLOOK.COM]”.
13:16:25 C: AUTH XOAUTH2 ••••••••••
13:16:31 S: 421 4.5.11 Too many authentication errors (4) on this 
connection, closing transmission channel. 
[YT1PR01CA0102.CANPRD01.PROD.OUTLOOK.COM]
13:16:31 Error: Unexpected return code 421 (expected 235):
“4.5.11 Too many authentication errors (4) on this connection, closing 
transmission channel. [YT1PR01CA0102.CANPRD01.PROD.OUTLOOK.COM]”.
13:16:31 C: AUTH XOAUTH2 ••••••••••
13:16:31 C: AUTH XOAUTH2 ••••••••••
```

**What I've tried**

* Deleting the oauth token (and refresh token) from my Keychain
* Removing and re-adding the Exchange account
* Changing my corporate password
* Reinstalling MailMate
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