In what order are users listed under Contacts?
Contacts are listed in the order of usage based on messages sent and calls made in Cliq and Chat Bar. (Check out Chat Bar at bottom of this page)
If you send just one message/call a user, they will get a usage count of 1 that day. So based on the highest usage count, the users will be listed under Contacts.
Say for example Scott posts an automated message daily to Olivia, and chats with Ryan frequently but not daily. So Olivia's count will be higher because a message is triggered everyday whereas Ryan's count gets updated only on days chat/call is established. Hence Olivia will be listed on top in Scott's Contacts followed by Ryan.
And this order will be retained for 90 days, post which the process will start again thereby removing inactive users from the list. If you are using Zoho Mail, then mails sent to a user will also be taken for the usage count.
This is the same order that will be populated everywhere for you – users listed for @ mentions, add participants view in group chat, frequent contacts in search box, ...
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Chat Bar is a mini version of Cliq that you can access across other Zoho Apps. Check out this page for more details - Chat Bar