The Rup dialects, or the Southeastern dialects, are a group of Bulgarian dialects located east of the yat boundary, thus being part of the Eastern Bulgarian dialects. The range of the Rup dialects includes the southern part of Thrace, i.e. Strandzha, the region of Haskovo, the Rhodopes and the eastern half of Pirin Macedonia. Before the Balkan wars and World War I, the Rup dialects covered a much larger territory, including vast areas of Eastern Thrace, Western Thrace and the eastern part of Greek Macedonia. Following the wars, most of the Bulgarian population in these areas fled or resettled to Bulgaria and nowadays, the Rup dialects outside Bulgaria are spoken only by the Muslim Bulgarians (Pomaks) in Western Thrace in Greece. Unlike the Northwestern or the Balkan dialects, the dialects included in the Rup group are not uniform and have vastly different phonological characteristics. What brings them together is the vast array of reflexes of Old Church Slavonic ѣ (yat). Whereas the Western Bulgarian dialects have only for yat in all positions and the Balkan dialects have or, depending on the character of the following syllable, the Rup dialects feature a number of different reflexes, none of which is similar to the ones in the Western Bulgarian or the Balkan dialects. These reflexes include: in all positions, broad е in all positions, before a hard syllable and broad e before a soft syllable, broad e in a stressed syllable and normal e in an unstressed syllable, etc. etc.
Read more about Rup Dialects: Phonological and Morphological Characteristics, Division of The Rup Dialects, Phonological and Morphological Characteristics of The "true" Rup Dialects, Phonological and Morphological Characteristics of The Rhodopean Dialects