MantisBT allows this

EmailReporting does not protect against this since most of the time this happens when users modify a document and keep mailing it to each other and modify it again and again until they are satisfied with the end result. In this situation you actually want every version of that document
Normal replies do not include the same attachment every time. Only forwards include the same attachment

Personally i see this more as an issue of instructing the users then something that EmailReporting should handle.

But what we could do is add a configuration option that allows you to tell EmailReporting that same name attachments should be replaced instead of renaming the new attachment and adding it another time.
If we do this would that be an end result that would be satisfactory?
Should EmailReporting log these replacements?

Please provide me your opinion on the above

EmailReporter should detect the same files in attachments. Or for example, if detected multiple pictures, provide link for it but not fully show.

What do you mean fully show? if it concerns the previews within an issue. That is fully handled by MantisBT and can be disabled if you so wish

I mean when picture appeares 1st time it have to be showed. For next time culd be good to have an option for disable its display.

The showing of the pictures is outside of the scope of this project and is completely handled by MantisBT

We are looking into ways to make sure duplicate attachments are not imported multiple times

Thanks. And onother one: how can i delete multiplied picture "sent" in html-code from reports?

Normal replies do not include the same attachment every time. Only forwards include the same attachment

Yes, if images are attachments.
But in most cases pictures are inline picture inside the html-style email's body. Therefore, when you reply html-style email, that pictures added by EmailReporter again and again.

Can EmailReporter check md5-hash (for example) for new attachments, compare with existing and do not add duplicates?

EmailReporting has an MD5 blocklist.
https://www.mantisbt.org/wiki/doku.php/mantisbt:plugins:emailreporting#mail_block_attachments_md5

This feature is meant to block some attachments altogether (for example pictures in signatures)
But at the moment it is not capable of checking the new attachments against existing attachments (for example using an md5 hash).

This is something we are looking into. But its complicated so will take some time

This feature is meant to block some attachments altogether (for example pictures in signatures)

Yes, I use this feature this way.

This is something we are looking into. But its complicated so will take some time

You can get all the attachments from the existing issue, count all hashes, exclude duplicates and after that add unique attachments to the new note. It looks not so complicated.

There is quite a bit of performance overhead to recalculating the hashes every time. So we are trying to find a solution to avoid that. I see that it has become a little easier since the FTP storage location has been deprecated. That would have been the most problematic one

But if its really that easy, i'm kinda wondering why you haven't coded it for us so that we can easily include it in EmailReporting. It would help us out a lot since we don't have a lot of time ourselves to code for this project.