In certain embodiments, a presentation of a user interface may be dynamically modified for a user based on data related to the user's email address or other user identifier. As an example, the user interface may be caused to reflect the look and feel of an interface of an entity trusted by the user, incorporate data items related to the user's identifier, or effectuate other modifications. In some embodiments, a user identifier of a user may be received via a user interface associated with the third party, and a query for data related to one or more user accounts associated with the user identifier may be generated. Based on the query, multiple datasets associated with different user accounts may be received, and a first dataset associated with a first account of the user may be selected over other datasets associated with the user's other accounts effectuate the presentation modification.