Yes, you can manually save the email address for the removed account as the secondary email address during the merge process. If you do not have access to the Secondary Email field, please contact support and request that the Secondary Email field be added to your database configuration.

Once you have access to the Secondary Email field and are merging a record,
  1. Select the record with the email address you want as the primary email to be the Master Record and click Next Step
  2. Click the Merge icon under the Duplicate Record heading
  3. Highlight and Copy the email you want to keep from the Duplicate Record and Paste it into the Secondary Email field in the Master Record
  4. Check the box beside other information you want to keep from the Duplicate Record, if any
  5. Click Save
When you complete the merge, Luminate Online will save the email from the Duplicate Record as the Secondary Email for the Master Record.

Related article: Can we send email to the secondary email?