Best way to add 500.000 subscribers to existing database. Can MC handle a peak from 1.500.000 to 2.000.000 in 12 hours or do you recommend loading new data in batches? To protect email reputation?

1 Answer 1


For large data volumes, you should use FTP to import subscribers. The wizard would not be appropriate. Create an Import activity under Interactions and it will let you specify the file name to look for in the FTP location. Splitting the file into smaller chunks will also work if it's manageable for you.

Know that imports will not impact the deliverability or the sender score (reputation). The sender score will be impacted if you decided to send an email to 500K subscribers all at once. If you're starting with a new implementation, it is recommended to follow the IP warming process to ensure your IP is ready for large volume sends.

  • Thanks ;o) Question 2. I have 240.072 rows - ca. 80mb what is suggested to import. Rest API og SFTP? for ongoing... May 2, 2017 at 13:43
  • I would recommend going with SFTP first, you could import a file and map it to a data extension. For working with REST API, you will have to write an external program to insert a record and then loop it over and over for each subscriber. May 10, 2017 at 15:36

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