Hello Steve, 

This very well could be a microsoft issue but to be on the safe side let's look at your SMTP and Delivery logs to make sure. You can either submit a ticket or we can review them here (sanitized for your protection ) 

Thank you

Tony

Hi Tony, 

There are no SMTP logs for the event as it fails to even hit our mail server.
The only logs show my successful email to the person that then received the email notification posted above when trying to write to me.

[2021.12.28] 13:10:58.850 [184.180.212.221][51623197] rsp: 220 mail.sgdesign.net Tue, 28 Dec 2021 21:10:58 +0000 UTC | SmarterMail Enterprise 16.3.0
[2021.12.28] 13:10:58.850 [184.180.212.221][51623197] connected at 12/28/2021 1:10:58 PM
[2021.12.28] 13:10:58.850 [184.180.212.221][51623197] Country code: US
[2021.12.28] 13:10:58.888 [184.180.212.221][51623197] cmd: EHLO smtpclient.apple
[2021.12.28] 13:10:58.888 [184.180.212.221][51623197] rsp: 250-mail.sgdesign.net Hello [184.180.212.221]250-SIZE 62914560250-AUTH LOGIN CRAM-MD5250-STARTTLS250-8BITMIME250-DSN250 OK
[2021.12.28] 13:10:58.934 [184.180.212.221][51623197] cmd: STARTTLS
[2021.12.28] 13:10:58.934 [184.180.212.221][51623197] rsp: 220 Start TLS negotiation
[2021.12.28] 13:10:59.166 [184.180.212.221][51623197] cmd: EHLO smtpclient.apple
[2021.12.28] 13:10:59.166 [184.180.212.221][51623197] rsp: 250-mail.sgdesign.net Hello [184.180.212.221]250-SIZE 62914560250-AUTH LOGIN CRAM-MD5250-8BITMIME250-DSN250 OK
[2021.12.28] 13:10:59.220 [184.180.212.221][51623197] cmd: AUTH CRAM-MD5
[2021.12.28] 13:10:59.220 [184.180.212.221][51623197] rsp: 334 PDEwMzI1NDMzMDguNjM3NzYyOTM4NTkyMjAxMTMxQG1haWwuc2dkZXNpZ24ubmV0Pg==
[2021.12.28] 13:10:59.266 [184.180.212.221][51623197] Authenticating as steve@sgdesign.com
[2021.12.28] 13:10:59.266 [184.180.212.221][51623197] rsp: 235 Authentication successful
[2021.12.28] 13:10:59.266 [184.180.212.221][51623197] Authenticated as steve@sgdesign.com
[2021.12.28] 13:10:59.304 [184.180.212.221][51623197] cmd: MAIL FROM:<steve@sgdesign.com>
[2021.12.28] 13:10:59.304 [184.180.212.221][51623197] senderEmail(1): steve@sgdesign.com parsed using: <steve@sgdesign.com>
[2021.12.28] 13:10:59.304 [184.180.212.221][51623197] rsp: 250 OK <steve@sgdesign.com> Sender ok
[2021.12.28] 13:10:59.304 [184.180.212.221][51623197] Sender accepted. Weight: 0. Block threshold: 30.
[2021.12.28] 13:10:59.351 [184.180.212.221][51623197] cmd: RCPT TO:<sandy@smartlevels.com>
[2021.12.28] 13:10:59.351 [184.180.212.221][51623197] rsp: 250 OK <sandy@smartlevels.com> Recipient ok
[2021.12.28] 13:10:59.389 [184.180.212.221][51623197] cmd: DATA
[2021.12.28] 13:10:59.389 [184.180.212.221][51623197] Performing PTR host name lookup for 184.180.212.221
[2021.12.28] 13:10:59.420 [184.180.212.221][51623197] PTR host name for 184.180.212.221 resolved as ip184-180-212-221.oc.oc.cox.net
[2021.12.28] 13:10:59.420 [184.180.212.221][51623197] rsp: 354 Start mail input; end with <CRLF>.<CRLF>
[2021.12.28] 13:10:59.552 [184.180.212.221][51623197] senderEmail(2): steve@sgdesign.com parsed using: Steve <steve@sgdesign.com>
[2021.12.28] 13:11:01.341 [184.180.212.221][51623197] rsp: 250 OK
[2021.12.28] 13:11:01.341 [184.180.212.221][51623197] Received message size: 1289799 bytes
[2021.12.28] 13:11:01.341 [184.180.212.221][51623197] Successfully wrote to the HDR file. (c:\SmarterMail\Spool\proc\1020736740037.hdr)
[2021.12.28] 13:11:01.341 [184.180.212.221][51623197] Data transfer succeeded, writing mail to 1020736740037.eml (MessageID: <5EFFD0C0-E807-4546-8B07-08DBF42BB269@sgdesign.com>)
[2021.12.28] 13:12:01.381 [184.180.212.221][51623197] cmd: QUIT
[2021.12.28] 13:12:01.381 [184.180.212.221][51623197] rsp: 221 Service closing transmission channel
[2021.12.28] 13:12:01.381 [184.180.212.221][51623197] disconnected at 12/28/2021 1:12:01 PM

Ok, The first part looks good. 

H Tony, 

Results from that search show:

[2021.12.28] 13:11:13.512 [36740037] Delivery finished for steve@sgdesign.com at 1:11:13 PM    [id:x1020736740037]