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Office 365 SMTP Authentication Error

Posted: Wed Nov 15, 2017 10:45 am
by ihandley
I am trying to configure my Cerberus FTP Server to send and receive email, but I keep getting the following error:

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SMTP server 'smtp.office365.com' tested: Failure on EHLO message to server - 535 5.7.3 Authentication unsuccessful [MWHPR15CA0063.namprd15.prod.outlook.com]
Here is the log message:

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2017/11/15 15:33:06	 [127]	 Failed authentication with SMTP server535 5.7.3 Authentication unsuccessful [MWHPR15CA0063.namprd15.prod.outlook.com]
2017/11/15 15:33:06	 [127]	 Unable to connect to SMTP server 'smtp.office365.com'
2017/11/15 15:33:06	 [127]	 [] SMTP server 'smtp.office365.com' tested: Failure on EHLO message to server - 535 5.7.3 Authentication unsuccessful [MWHPR15CA0063.namprd15.prod.outlook.com]
I've searched the forums as well as the rest of the interweb for a solution to no avail. Please help!

Thanks in advance!

Re: Office 365 SMTP Authentication Error

Posted: Thu Nov 16, 2017 10:26 am
by pacman
Hi,

The problem is that the Microsoft server does not support the cipher suites you've selected for your SSL cipher string.

The Microsoft SMTP server does not support any of the perfect forward secrecy suites at the 256 bit encryption level.

You can use the following cipher string to connect to Microsoft's SMTP server with 256 bit encryption: (Configure>Security>Advanced)

ALL:!LOW:!EXP:!aNULL:!RC4:!3DES:!AES128:!RC4:!SEED:!CAMELLIA128:!IDEA:@STRENGTH

This will allow negotiation of the non-perfect forward secrecy suites that the Microsoft server supports at the 256 bit encryption level.