A system comprising: one or more hardware processors; and a memory storing instructions that, when executed by the one or more hardware processors, causes the one or more hardware processors to perform operations comprising: obtaining subscriber information for each user of a collaboration system, the subscriber information corresponding to one or more features of content that are relevant to each user, wherein the subscriber information comprises one or more indications of: (a) a site to obtain content that corresponds to a site identifier, (b) a topic indicated to be relevant that corresponds to a topic identifier, or (c) an audience that each user is a member of that corresponds to an audience identifier; hashing, using at least one hashing function, the subscriber information to generate a bloom filter for each user; receiving an article to be published, the article comprising a set of features; hashing, using the at least one hashing function, the set of features to obtain a hash set for the article; comparing the hash set to the bloom filter for each user to identify a match, the match indicating a feature of the article matching the subscriber information; generating a list of recipients based on the match; invoking a distribution pipeline to send a notification to each user on the list of recipients; causing a control flow message to be sent to an email server of each user on the list of recipients; in response to receiving the control flow message, verifying, at the email server of a user, that subscriber information for the user matches at least one feature of the article; and in response to the verifying, sending the notification to a user device of the user. one or more hardware processors; and a memory storing instructions that, when executed by the one or more hardware processors, causes the one or more hardware processors to perform operations comprising: obtaining subscriber information for each user of a collaboration system, the subscriber information corresponding to one or more features of content that are relevant to each user, wherein the subscriber information comprises one or more indications of: (a) a site to obtain content that corresponds to a site identifier, (b) a topic indicated to be relevant that corresponds to a topic identifier, or (c) an audience that each user is a member of that corresponds to an audience identifier; hashing, using at least one hashing function, the subscriber information to generate a bloom filter for each user; receiving an article to be published, the article comprising a set of features; hashing, using the at least one hashing function, the set of features to obtain a hash set for the article; comparing the hash set to the bloom filter for each user to identify a match, the match indicating a feature of the article matching the subscriber information; generating a list of recipients based on the match; invoking a distribution pipeline to send a notification to each user on the list of recipients; causing a control flow message to be sent to an email server of each user on the list of recipients; in response to receiving the control flow message, verifying, at the email server of a user, that subscriber information for the user matches at least one feature of the article; and in response to the verifying, sending the notification to a user device of the user. obtaining subscriber information for each user of a collaboration system, the subscriber information corresponding to one or more features of content that are relevant to each user, wherein the subscriber information comprises one or more indications of: (a) a site to obtain content that corresponds to a site identifier, (b) a topic indicated to be relevant that corresponds to a topic identifier, or (c) an audience that each user is a member of that corresponds to an audience identifier; hashing, using at least one hashing function, the subscriber information to generate a bloom filter for each user; receiving an article to be published, the article comprising a set of features; hashing, using the at least one hashing function, the set of features to obtain a hash set for the article; comparing the hash set to the bloom filter for each user to identify a match, the match indicating a feature of the article matching the subscriber information; generating a list of recipients based on the match; invoking a distribution pipeline to send a notification to each user on the list of recipients; causing a control flow message to be sent to an email server of each user on the list of recipients; in response to receiving the control flow message, verifying, at the email server of a user, that subscriber information for the user matches at least one feature of the article; and in response to the verifying, sending the notification to a user device of the user.