The web service correspSearch aggregates metadata of letters from printed and digital scholarly editions and publications. It offers the aggregated correspondence metadata both via a feature-rich interface and via an API. The letter metadata are provided by scholarly projects of different institutions in a standardised, TEI-XML-based exchange format and and by using IDs from authority files (GeoNames, GND, VIAF etc.). The web service itself does not set a spatial or temporal collection focus. Currently, the time frame of the aggregated correspondence data ranges from 1500 to the 20th century.