Above 4 MB attachment Mails getting sent multiple times, Outlook sent items does not show sent mail where as Zoho sent items show multiple entries

Above 4 MB attachment Mails getting sent multiple times, Outlook sent items does not show sent mail where as Zoho sent items show multiple entries

Hi, when I am trying to send any mail with an attachment (file size above 4MB), it gets sent to recipient multiple times. the mail is also shown in Zoho sent items for the multiple times but at the same time it is not shown in outlook sent items and shows in outbox. this is happening since 10 days and it is really annoying when it gets hit at Client's mail box multiple times.

i actually have to delete the mail from outbox after i see the ZOHO sent items (whr it shows the mail sent multiple times).

have even deleted unwanted mails in last few days to make more space for the account but the problem still remains same!

sincere request to look into the matter as my client service is badly affected.

best regards,