We are seeing the same issue. We have an open ticket on this problem. 

Today I had time to carry out further tests and it SEEMS that the disappearance of the emails has a dependency: depending on which is the starting mail system of the emails.

In my case I tested from MS Exchange OVH hosted, Libero Mail - an Italian provider -, OUTLOOK.COM (all of these via my Outlook on my PC).

I also tried the GMAIL webmail and the webmail of my SmarterMail server.

Well, I discovered this:

- e-mails sent with the OUTLOOK.COM account, if they are moved, practically always disappear

- e-mails sent with the LIBERO MAIL account, if they are moved, disappear often, but not always

- e-mails sent via the Smarter Mail server, if they are moved, NEVER disappear!

- if the e-mails sent via the GMAIL webmail are moved they do NOT seem to disappear

- e-mails sent via OVH hosted Exchange if they are moved do not seem to disappear

So the problem needs to be investigated further and you have to do more tests because it seems that SmarterMail behaves differently depending on the origin of the emails.

Probably some providers do something inside the headers or the content of the mails that SmarterMail DOES NOT LIKE and that therefore triggers the disappearance of the mail when moving from one account to another.

Hello Gabriele :-) I followed up on your ticket with Zach with these results but wanted to update here as well in case other users are wondering too. I did some testing using your results as my reference, and was able to get this partially reproduced using messages from Outlook.com. This should give us something to go on, so I'm working on getting this escalated to development for review now.

I asked Gabriele if he could need help in testing/verifiying /if other SmarterMail customers are seeing such a strange behavior at Outlook/MAPI-move from one acocunt to another/seond account. He sent my 16 test-emails to a test-acocunt, setup in Outlook2019/MAPI. I moved these 16 emails one by one to another test-account configrued at same Outlook 2019 and MAPI-protocol.
First all 16 messages moved to the other account and showed up inside that accounts "Inbox" where I moved it into.
Then I closed/quit Outlook 2019 - re-opened Outlook - and then only 15 of priot 16 messags were showing up inside that account (for Insiders: missing was just 'LiberoMail (with Outlook IMAP) test 2'.).
I deviced to close/quit Outlook again - and re-opened it - and then only 4 emails are left - the emails that did not "disappear" were (again for Insiders) 'OVH Exchange acocunt test 1,2,3 and 4.'

I checked the acocunt at SmarterMail/Webmail: even there only the four messages of total/original 16 messages are showing up - 12 emails are being "lost in space" or whereever :-( It really looks like Gabriele is right that there is an issue inside SmarterMail Build 8223 with more than one MAPI-account inside Outlook-client configured and moving messages between these accounts! And kind of "fatal" that these emails are being "lost/vanished". I will open a support-ticket by myself probably tomorrow - so I will have some more time to do some internal testing. In case of custom build avaiable for testing a fix please give me an info.

Regards,
Thomas

Hi Thomas!

Thanks for your help and time testing it with me, I really appreciate it

@ Kyle:   thx! I hope this issue will be fixed soon, it's a real pain to know that some mails can disappear without notice...

Very welcome and happy to help out. Half the battle is getting the issue reproduced so we're definitely headed in the right direction now.

Hi all, 

While we're investigating this issue, I strongly encourage you to configure Message Archiving for your domains. Message Archiving allows incoming / outgoing email to be stored in a separate location on the server, and the email is archived as soon as it hits the spool. Mail can be restored to a user's mailbox directly from the Archive Search. While it's certainly not a solution for this problem, it can help mitigate data loss. 

@Andrea: Good hint to mention that feature to save/keep the original messages.

We are already using SmarterMail´s 'Message Archiving' and in additon "MailStore Server" as an additional/separate email-archiving solution. To figure out which emails we probably lost by moving into another user/email-account - what can we do? Can we see this "unwanted deletion" inside a specific logfile? What logs shoudl we set to detailed to figure out what could be missing/lost by/after moving?

Hi all, 

I wanted to let you know that this issue was resolved in Build 8250 (Aug 3, 2022). Please upgrade if you're still experiencing this issue. 

Kind regards,