Microsoft recently increased the message size limit for Office 365 from 25MB to 150MB. This increase is not applied to every Office 365 plan.
In particular, the Office 365 tenant you are migrating into has the limit increased to 150MB.
However, you are still unable to migrate a message that is larger than 25 MB.
The increased limit of 125 MB applies to move based migrations using any supported Exchange Mailbox Replication Service and NOT to 3rd party tools.
On Demand Migrator for Email (ODME) is a 3rd party tool. Therefore, ODME is limited by general message size limit of 25 MB.
Refer to Microsoft article: "Exchange Online Limits - Message Limits Across Office 365 options", Note 4.