This is what a good log entry made by thunderbird looks like: I wrestled with authentication until I realized the email address I was trying to use for authentication wasn't the actual mailbox email account. Unable to send emails using C# code from GoDaddy configured … root, exim, and mailman are still allowed to make direct connections. Another possibility is basic authentication was disabled for the user/tenant/protocol. In 2022, we plan to disable those older TLS versions to secure our customers and meet compliance requirements. In the Email apps section, click Manage email apps. VB.NET/ASP.NET/ASP MVC - Send Email using Microsoft OAuth … Last year, we announced that we would enable OAuth 2.0 support for IMAP, SMTP AUTH protocols and retire Basic Authentication access to Exchange Online mailboxes.. Today, we’re announcing the availability of OAuth 2.0 authentication for IMAP, SMTP AUTH protocols to Exchange Online mailboxes. Port: 587 Type of Encrypted Connection: SSL Outgoing Mail (SMTP) Server: smtp.office365.com Port: 465 Type of Encrypted Connection: SSL. an e-mail sender) to log on to an SMTP server (i.e. Server name: outlook.office365.com. Fix - The SMTP server requires a secure connection or the client … Since it was working previously, possibly you’ve changed some settings within your Microsoft account. The server response was: 5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM; MAIL KIT IMPLEMENTATION (suggestion of vasily.sib) Using Microsoft/Office 365 OAUTH + EWS and Ms Graph API Microsoft Office365 EWS and Ms Graph API servers have been extended to support authorization via the industry-standard OAuth 2.0 … To check if the SMTP service is working fine, please set up the account via POP/IMAP in the Outlook client and check if you can successfully send a test email using the Outlook client. Blog Office365 SMTP: 5.7.57 SMTP; Client was not … O365 SMTP Auth upcoming changes : Office365 - reddit