In Method, you are unable to locate the email adress field in the "OtherName" table.  In QuickBooks Desktop for the "Other Names" list you are able to add an email address for the "Other Name" entity type.    This is a known QuickBooks SDK limitation.

Resolution

QuickBooks allows you to enter an email address for the entity type "Other Name".  However when you work with 3rd party applications that talk to QuickBooks like Method Integration, you'll notice this field is not accessible.  This is not a limitation of Method or any 3rd party application but rather a limitation of the QuickBooks SDK.  Intuit would need to add this field to the SDK in order for us to be able to view/edit the field in Method.  At this point in time they have not provided any indication that the field will be added.

Adding your own email address field

Since Method allows for you to add you own custom fields to any table, you can add you own email address field to the OtherName table.  Keep in mind that while you can add/view/edit/delete the contents of this field in Method, it will not sync over to QuickBooks.  

To add an email address field to your Method account, follow the steps below.

1. Click Customize > Tables / Fields.
2. Click Edit Fields... for the "OtherName" table.
3. In the Field Name box, type in Email.
4. For the Field Type dropdown, select Text.
5. In the Size box, you can keep the default of 255.
6. Click Add Field.