On my own account, Plus Addressing is set to Move to Folder (if Exists). I don't see this with all, but several emails will be delivered to both the destination folder, as well as inbox for the same email. Not a major issue, but I don't see it reported yet. The sending device authenticates under a general notification account, and then sends "from" myself on the same domain. Many devices do this, only some duplicate that are setup this way (in case that was a question). It's not really consistent that I can tell, other than it seems that Veeam Agent backup reports seem to be the ones to do this the most if that helps trying to duplicate or narrow things down.

This is for build 8895

SMTP -

[2024.05.15] 10:16:30.893 [x.x.x.x][63682285] rsp: 220 mail.xxx.com
[2024.05.15] 10:16:30.893 [x.x.x.x][63682285] connected at 5/15/2024 10:16:30 AM
[2024.05.15] 10:16:30.893 [x.x.x.x][63682285] Country code: US
[2024.05.15] 10:16:30.932 [x.x.x.x][63682285] cmd: EHLO Laptop
[2024.05.15] 10:16:30.934 [x.x.x.x][63682285] rsp: 250-mail.xxx.com Hello [x.x.x.x]250-SIZE 139810133250-AUTH LOGIN CRAM-MD5250-STARTTLS250-8BITMIME250-DSN250 OK
[2024.05.15] 10:16:30.973 [x.x.x.x][63682285] cmd: STARTTLS
[2024.05.15] 10:16:30.973 [x.x.x.x][63682285] rsp: 220 Start TLS negotiation
[2024.05.15] 10:16:31.120 [x.x.x.x][63682285] cmd: EHLO Laptop
[2024.05.15] 10:16:31.122 [x.x.x.x][63682285] rsp: 250-mail.xxx.com Hello [x.x.x.x]250-SIZE 139810133250-AUTH LOGIN CRAM-MD5250-8BITMIME250-DSN250 OK
[2024.05.15] 10:16:31.165 [x.x.x.x][63682285] cmd: AUTH login x
[2024.05.15] 10:16:31.165 [x.x.x.x][63682285] Authenticating as notifications@xxx.com
[2024.05.15] 10:16:31.165 [x.x.x.x][63682285] rsp: 334 x
[2024.05.15] 10:16:31.209 [x.x.x.x][63682285] rsp: 235 Authentication successful
[2024.05.15] 10:16:31.209 [x.x.x.x][63682285] Authenticated as notifications@xxx.com
[2024.05.15] 10:16:31.249 [x.x.x.x][63682285] cmd: MAIL FROM:<xxx+z@xxx.com>
[2024.05.15] 10:16:31.251 [x.x.x.x][63682285] senderEmail(1): xxx+z@xxx.com
[2024.05.15] 10:16:31.251 [x.x.x.x][63682285] rsp: 250 OK <xxx+z@xxx.com> Sender ok
[2024.05.15] 10:16:31.251 [x.x.x.x][63682285] Sender accepted. Weight: 0. Block threshold: 25.
[2024.05.15] 10:16:31.292 [x.x.x.x][63682285] cmd: RCPT TO:<xxx+z@xxx.com>
[2024.05.15] 10:16:31.293 [x.x.x.x][63682285] rsp: 250 OK <xxx+z@xxx.com> Recipient ok
[2024.05.15] 10:16:31.334 [x.x.x.x][63682285] cmd: DATA
[2024.05.15] 10:16:31.335 [x.x.x.x][63682285] Performing PTR host name lookup for x.x.x.x
[2024.05.15] 10:16:31.335 [x.x.x.x][63682285] PTR host name for x.x.x.x resolved as x
[2024.05.15] 10:16:31.337 [x.x.x.x][63682285] rsp: 354 Start mail input; end with <CRLF>.<CRLF>
[2024.05.15] 10:16:31.382 [x.x.x.x][63682285] senderEmail(2): xxx+z@xxx.com parsed using: xxx+z@xxx.com
[2024.05.15] 10:16:31.429 [x.x.x.x][63682285] DMARC Results: Skipped (Authenticated), Reason: Unknown, Reject? False
[2024.05.15] 10:16:31.429 [x.x.x.x][63682285] rsp: 250 OK
[2024.05.15] 10:16:31.431 [x.x.x.x][63682285] Received message size: 15798 bytes
[2024.05.15] 10:16:31.432 [x.x.x.x][63682285] Successfully wrote to the HDR file. (c:/SmarterMail/Spool/SubSpool4/624429413.hdr)
[2024.05.15] 10:16:31.432 [x.x.x.x][63682285] Data transfer succeeded, writing mail to 624429413.eml
[2024.05.15] 10:16:31.616 [x.x.x.x][63682285] disconnected at 5/15/2024 10:16:31 AM

Delivery -

[2024.05.15] 10:16:33.229 [24429413] Delivery started for xxx+z@xxx.com (via notifications@xxx.com) at 10:16:33 AM
[2024.05.15] 10:16:33.231 [24429413] Added to SpamCheckQueue (1 queued; 0/5 processing)
[2024.05.15] 10:16:33.231 [24429413] [SpamCheckQueue] Begin Processing.
[2024.05.15] 10:16:33.231 [24429413] Blocked Sender Checks started.
[2024.05.15] 10:16:33.232 [24429413] Blocked Sender Checks completed.
[2024.05.15] 10:16:33.249 [24429413] Spam Checks started.
[2024.05.15] 10:16:33.249 [24429413] Spam Checks skipped: User authenticated
[2024.05.15] 10:16:33.249 [24429413] Spam Checks completed.
[2024.05.15] 10:16:33.533 [24429413] Removed from SpamCheckQueue (0 queued or processing)
[2024.05.15] 10:16:36.230 [24429413] Added to LocalDeliveryQueue (1 queued; 0/50 processing)
[2024.05.15] 10:16:36.230 [24429413] [LocalDeliveryQueue] Begin Processing.
[2024.05.15] 10:16:46.262 [24429413] Starting local delivery to xxx@xxx.com
[2024.05.15] 10:16:46.276 [24429413] Delivery for xxx+z@xxx.com to xxx@xxx.com has completed (Delivered to z) Filter: None
[2024.05.15] 10:16:46.276 [24429413] End delivery to xxx@xxx.com (MessageID: <60c8f326835348b5b6b3c20ae952f698@1e8473565f9f4e8b9faf551c75eb92cb>)
[2024.05.15] 10:16:46.276 [24429413] Starting local delivery to xxx@xxx.com
[2024.05.15] 10:16:46.279 [24429413] Delivery for xxx+z@xxx.com to xxx@xxx.com has completed (Delivered) Filter: None
[2024.05.15] 10:16:46.279 [24429413] End delivery to xxx@xxx.com (MessageID: <423b6ba59ae84509aeeb90d9c57a28b5@f334b973f65349dc9cb7c5cfce575a82>)
[2024.05.15] 10:16:46.280 [24429413] Removed from LocalDeliveryQueue (0 queued or processing)
[2024.05.15] 10:16:48.246 [24429413] Removing Spool message: Killed: False, Failed: False, Finished: True
[2024.05.15] 10:16:48.246 [24429413] Delivery finished for xxx+z@xxx.com at 10:16:48 AM    [id:624429413]