The leaf level of the clustered index is the in-row data, logically ordered by the clustering key.

78,000 rows of ~50KB emails comes to around 3.6GB data in total.

With overhead (row headers, unused space within pages), your situation is within the bounds of what would be expected.

See Estimate the Size of a Clustered Index in the documentation.

Presumably, your local testing was done with smaller, non-production data.

The leaf level of the clustered index is the in-row data, logically ordered by the clustering key.

78,000 rows of ~50KB emails comes to around 3.6GB data in total.

With other row data, and overhead (row headers, unused space within pages), your situation is within the bounds of what would be expected.

See Estimate the Size of a Clustered Index in the documentation.

Presumably, your local testing was done with smaller, non-production data.