Synonyms:
- Pastoral Epistle,
- aerogram,
- air letter,
- airgraph,
- bull,
- chain letter,
- dead letter,
- dimissorial,
- dimissory letter,
- drop letter,
- encyclical,
- fan letter,
- form letter,
- letter of credit,
- letter of introduction,
- letters credential,
- letters of marque,
- letters of request,
- letters overt,
- letters patent,
- letters rogatory,
- love letter,
- mash note,
- monitory,
- newsletter,
- nixie,
- open letter,
- pastoral letter,
- poison-pen letter,
- round robin,
- valentine