Gmail on Outlook sending multiple emails with attachment

An email is sent once but multiple Sent items appear at an interval of five minutes for as many as fourteen copies.

We noticed that this only happens when the email has an attachment of more than 24 MB (whether or not just one file)

In addition, Gmail should only allow a 25 MB email size (i.e. total file size of an email including body and attachment/s) but these emails go through and getting received by the recipient/s even for emails amounting to as much as 40 MB