Why are some contacts duplicated after synchronization?

Basically, sync.blue® works with a sophisticated mechanism that almost avoids this.

Possible reasons

However, some causes can never be avoided with unconventional address book maintenance:

• The contact has neither an email address nor a first and last name (each in its own field).
• The contact has no email address and the "First name" field was filled with "First and last name" or a company name.
• For sync target "Microsoft 365 Exchange Online": The contact was manually deleted in the sync target at the same time along with many other contacts and a full sync was started immediately afterwards (the reason is very slow processing of mass changes by the Microsoft API).

Support

If none of the above reasons explain the contact duplicates, please send us a screenshot of an example contact in both the sync source and sync target so that we can analyze the situation.