Snail Mail is for quickly addressing and printing single or multiple envelopes on Mac OS X
Last Version 1.8 Released in 2011 - seems to still launch on 10.12.6
https://github.com/downloads/knowuh/SnailMail/SnailMail-1.8.0.zip
https://github.com/knowuh/SnailMail/downloadsSnail Mail
Snail Mail's primary function is to quickly address and print single or multiple envelopes based on entries in the Mac OS X Address Book database, but it also allows ad-hoc manual entry of addresses directly onto the envelope.
Batches of envelopes can be based on Address Book groups, or ad-hoc selections of addresses. Snail Mail can print USPS barcodes for more efficient mail handling. Snail Mail provides for different default text attributes (font, colour, etc) for different parts of the address.
Snail Mail also includes a Plugin for Mac OS X's Address Book application so that you can choose to print Snail Mail envelopes directly from the Address Book, and uses Mac OS X 'services' to print any selected text from any other application to an envelope quickly and easily.
Click here to download Snail Mail (from the new GitHub project site which is not managed by NIXANZ).
NB: Snail Mail is no longer supported or maintained by NIXANZ, but has been open sourced.
https://github.com/knowuh/SnailMail
https://github.com/knowuh/SnailMail/downloads