When you send an email to a client/supplier through LSP.expert, the system uses by default the first name and last name of the client or supplier (e.g. 'Dear John Smith, ...').
If you would like your emails to only mention the first name of the person ('Dear John, ...') or a friendly name you always use to call this person (e.g. 'Dear Bob, ...' for someone called Robert), you can define it in the Friendly name field of the contact under Clients > click on the client concerned > Contacts > Edit the contact concerned.
When sending an email, the system will use the friendly name you defined in the client's details:
To change the text of the emails you send using LSP.expert, see this article: http://help.lsp.expert/documents/where-can-i-changecustomize-the-text-of-the-emails-i-send-with-lspexpert