I have integrated a mailbox into a web application that is supposed to act as a helpdesk. I can successfully send emails from the app via SMTP. However, I cannot fetch any incoming mails from users. The app can successfully establish a connection to the server (via a button saying "test connection"), but is unable to load any mails. In the logs, the following error is thrown:

Error: imap_open(): Couldn't open stream {xxxxxx:143/imap/novalidate-cert}. Retrying CRAM-MD5 authentication after AUTHENTICATE login failure: user name or password rejected; Can not authenticate to IMAP server: [CLOSED] IMAP connection broken (authenticate); File: /www/html/overrides/webklex/laravel-imap/src/IMAP/Client.php (230)

As can be seen, to fetch e-mails, I am using IMAP and port 143 for unencrypted communication. As for the credentials, I used the standard credentials to this mailbox. For sending mails they are working just fine.

Does anyone have an idea about the cause of the above error and where to look at to solve this issue?

CodePudding user response：

We migrated to another mail server, which solved the issue. I still don't know what caused the error. We could see from logs of both the mail server and the application that there was a successful connection.