Of the 214 letters in the collection, 213 are addressed to Cardinal Lorenzo Magalotti, while the final letter is addressed to Cardinal Francesco Barberini, a nephew of both Magalotti and Pope Urban VIII (Maffeo Barberini) from Carlo de’ Medici. The collection dates from 1623, from the years preceding Magalotti’s ordination as cardinal to the months preceding his death in September 1637. One hundred and seventeen letters date to the period prior to Magalotti’s appointment as Bishop of Ferrara, which was then under the direct control of the papacy. Despite the collection being nearly divided in number between these two phases of his life, the content of the letters reflects Magalotti’s transition from Papal Secretary of State to Bishop of Ferrara. In comparing the letters Magalotti received before accepting his bishopric to those he received afterwards, this transition is clear. The number of letters of recommendation Magalotti received decreased from 42 to a mere 14. Meanwhile, the number of thank you notes increased from 27 to 50. Even the content of the thank you letters reflects this, as the gratitude offered within the letters shifts from gratitude primarily for political favors granted to gratitude for personal ones. Within this subcategory of thank you letters, however, is a surprising amount which thank Magalotti for his invitation to a Christmas Feast. There are 23 of these in total, yet 18 of them are dated 1628 or later. Despite many of these letters having originated from the family of the Grand Duchy of Tuscany, they nevertheless account for approximately a tenth of the collection.

Within this collection are letters addressed to Magalotti from 33 correspondents, yet the majority of letters originate from the family of the Grand Duchy of Tuscany. Forty-six were written by Ferdinand II de’ Medici, Grand Duke of Tuscany (r. 1621-1670), whose letters date from November 1624 to April 1637. His rule was marked by the co-regency of both his paternal grandmother, Christina of Lorraine, and his mother, Maria Maddalena of Austria. Both Christina of Lorraine and Maria Maddalena corresponded with Magalotti as well, having written 27 and 24 letters, respectively. Their regency over Ferdinand lasted until 1629, at which point the content of their letters become more personal in nature. Christina of Lorraine’s letters date from June 1623 to December 1635, while Maria Maddalena’s date from January 1624 to October 1631. There is a large gap in Christina’s letters dating from April 1629 to July 1631. Almost half of Christina of Lorraine’s letters are letters of recommendation for individuals, some of whom sought political offices. Meanwhile, although Maria of Maddalena also sent Magalotti letters of recommendation throughout the length of their correspondence, her letters include more personal accounts than those of her co-regent. Her final letters to him concern a request for advice regarding travelling, as Maria wished to visit her brother, and one letter from 22 September 1631 mentions that Maria fears that she is becoming ill. Her last letter to Magalotti dates 1 October 1631, one month before her death.

Additionally, Leopold V, Archduke of Austria (Maria Maddalena’s brother), wrote 12 letters to Magalotti, dating from January 1626 to July 1629. He is consistent with his spacing between letters, and the letters themselves contain an even blend of political requests and personal anecdotes and news, such as one letter from May 1628 (immediately after Magalotti’s exile to Ferrara), in which Leopold thanks Magalotti for his congratulations offered at the birth of Leopold’s first son. Magalotti also received 28 letters from Vladislav IV Vasa of Poland (r. 1632-1648). The vast majority of these letters contains either requests for assistance or recommendations. The first 14 letters date from 1625 to August 1626, while the latter fourteen date from November 1632 to June 1637. The first letter of this second phase is from the day immediately following Vladislav IV’s coronation as King of Poland, 9 November 1632. There are no letters in the collection from Vladislav written during 1636. The gap from 1626 to 1632 may be attributed in part to Vladislav IV ‘s time in the Polish-Swedish War. It is worth noting, however, that Vladislav’s father, Sigismund III Vasa, corresponded with Magalotti from 1626 to 1630 with five letters of his own.

Magalotti also received fewer than ten letters from each of the following individuals: Albert VI of Bavaria; Nicholas II (Nicholas Francis), who had recently abdicated his rule as Duke of Lorraine; Henry II, Duke of Montmorency; Elizabeth of France, queen consort of Spain and wife of King Philip IV of Spain; Margaret of Savoy, Vicereine of Portugal; Melchior Mitte de Chevrières, Marquis de St. Chamond; Zaga Christo (Saga Krestos), the exiled son of the former Ethiopian emperor Yaqob I (whose regal name was Malak Sagad II); Michael Adolph von Althann, Count of Althann; Anselm Casimir Wambold von Umstadt, Archbishop of Mainz. There are additionally two letters in the collection addressed to Magalotti from Carlo de’ Medici, mentioned above. The collection also contains fewer than ten letters from the following: Claudia de’ Medici, Archduchess Consort of Austria; Johannes Lemgovius, Deacon of the Cologne Cathedral; Constantius Francet (?), and the Consuls and Senators of the City of Cologne; Eleonora Gonzaga; Empress of Ferdinand II; Ferdinand II, Holy Roman Emperor; Ferdinand III, Holy Roman Emperor; Ferdinand of Bavaria, Archbishop and Prince-Elector of Cologne; Hildebrand, Bishop of Sion; Isabella Clara Eugenia, wife of Archduke Albert of Austria (the Governor of the Spanish Netherlands); Louis XIII, King of France; Marie de’ Medici, wife of Henry IV and Queen Consort of France; Matthew (?) of St. Germain-des-Prés; Maximilian I, Duke and Elector of Bavaria; Ranuccio Pauli; Philip IV, King of Spain; Richard Smith, Bishop of Chalcedon; and, Wolfgang William, Count Palatine of Neuberg.