Mailability

Mailability is the property of a mailitem or message that determines whether it is eligible for transmission through a postal system or an electronic mail channel. In a postal context, mailability encompasses the physical characteristics and regulatory compliance required for acceptance, processing, and delivery by the carrier. In the digital realm, mailability refers to the likelihood that an email will reach the recipient’s inbox rather than be blocked or flagged as spam.

For physical mail, common criteria include dimensions and weight within published ranges, shape suitable for automated processing, and the ability to bear a legible recipient address. The piece should include a valid postage payment method and appropriate markings or barcodes for sorting and tracking. Materials should be nonhazardous and securely packaged; items that are oversized, unusually rigid, or have irregular folds may be considered nonmachinable or non-mailable. International mail adds additional requirements such as country-specific labeling, customs declarations, and transit restrictions.

With email, mailability depends on deliverability factors such as sender reputation, authentication (SPF, DKIM, DMARC), list quality, and engagement signals. Compliance with anti-spam laws and privacy regulations, explicit opt-in, easy unsubscribe options, and accurate address data improve outcomes. Content quality, sending cadence, and accurate header information help avoid spam filters and improve inbox placement. Ongoing monitoring of bounces, complaints, and feedback loops supports sustained mailability.