Note for OTRS emails fetched from third Party software

[sunny]

We are facing a challenge and unable to find the reason and solution

OTRS (3.2.16) is fetching emails from third party software like Exchange/ Gmail etc using POP/IMAP...
Need to know how OTRS determines that an email has been successfully downloaded and that the next OTRS fetch will not download the same email again. Also, if OTRS fetch is partially downloaded an email and the process fails to complete, how can OTRS determine to fetch the same email again, to complete the process. Observed that partially fetched emails are left out in the next fetch cycle, resulting in emails being missed out. (ie. Email received in third party server but not in OTRS)

Please help!

[jojo]

emails will be downloaded and deleted. if a fetch fails otrs will attempt to download all mails again

[sunny]

But as in our case we are using GMAIL as POP3S and done the settings in "Forwarding and POP/IMAP" ->
When messages are accessed with POP -> keep Gmail's copy in the Inbox

so emails will not be deleted after downloading, please suggest what would happen then

[jojo]

I can not tell, as I have to expect that they will be deleted as desinged in OTRS