Usually, when you sent an email from a IMAP email client, the sent copy will be stored in a local Sent folder on your device by default. It implies that those emails will not be saved on the email server and you cannot access them from another device or any other IMAP email client as well. Not only the Sent folder, there are also 3 kinds of special folders such Trash, Drafts and Junk which will be associated to the related local IMAP folders by default.
In order to solve this issue, some IMAP email clients can allow you to associate the special IMAP folders with the server ones individually. Noted that some IMAP email clients may not provide any or all folders association option. It depends on the design of IMAP email client.