Keep the mailbox identifier intact#
Domain names can be normalized without rewriting the local part. Provider-specific handling of case, dots and plus tags is not a universal rule. A transformation that works for one mailbox provider can be wrong for another.
Make merge rules explicit#
MailMaid preserves local-part case and plus tags while normalizing the domain. Its duplicate flag identifies the same resulting address, not two contacts who merely look similar. Keep contact IDs when a single mailbox belongs to several business records.
Review before collapsing records#
Decide whether the task is deduplicating a send audience or merging CRM people. Those are different operations. One can prevent repeated sends without destroying distinct customer, subscription or consent records. Use a sample export to confirm the behavior before processing an important audience.