IMAP Limitations?

Hi

I am in the progress of migrating my old Outlook emails into ZOHO.

I have set up an IMAP account within Outlook for ZOHO. To migrate my emails, I am draging folders from my Outlook PST file account into my IMAP ZOHO account.

This method has worked ok, but one thing I have noticed is that it doesn't seem possible to sync back to ZOHO emails larger than around 7MB.

Is is possible however, to receive emails greater than 10MB in my IMAP ZOHO account in Outlook.

Can someone please advise me why there is a smaller limit syncing back to ZOHO via IMAP?