MailStream Plus™, all versions, all platforms
There are two types of First-Class Mail Attachments and Enclosures- Incidental and Nonincidental. In the USPS DMM (Domestic Mail Manual), the definitions and regulations are in sections 243 2.5.2 and 2.5.3/2.5.4 respectively. (Current as of August 2019)
Currently, MailStream Plus™ supports 'Incidental' Attachments and Enclosures, which are ones where there is no additional First-Class postage required. The postage at the USPS Marketing Mail price for the attachment or enclosure is based on the combined weight of the host piece and the incidental First-Class Mail attachment or enclosure.
The parameter that controls this type of mailing is P ATTR position 68
Currently, MailStream Plus™ supports 'Incidental' Attachments and Enclosures, which are ones where there is no additional First-Class postage required. The postage at the USPS Marketing Mail price for the attachment or enclosure is based on the combined weight of the host piece and the incidental First-Class Mail attachment or enclosure.
The parameter that controls this type of mailing is P ATTR position 68
UPDATED:
August 28, 2019