I am using Mailkit to programmatically retrieve email messages from email accounts. Is there a standard way using IMAP to retrieve the email account logo/avatar for example from Gmail using MailKit? Does IMAP define avatar for email accounts?
The core IMAP protocol has no support for avatars.
What you are probably looking for is Gravatar which uses an email address (or login name) as a key for looking up a globally hosted avatar.
You can query their service using an email address as a key and get back an avatar if the user has created one and uploaded it to their service.