Issues with SMTP and Office365

  • Resolved alexqbox

    (@alexqbox)


    1 week, 1 day ago

    On several websites, we are experiencing an issue where emails cannot be sent using either SMTP or Office 365.

    The SMTP connection itself is established successfully, but when attempting to send a test email, nothing happens. Instead, the browser console reports an HTTP 500 error for /wp-admin/admin-ajax.php. Same experiences with Office365.

    Additionally, the browser console displays an error originating from the FluentSMTP plugin, indicating that WordPress is not returning a valid response. The underlying error should be visible in the server logs or WordPress debug logs at the time the form or test email is submitted.

    The same issue also affects all contact forms on the website, as form submissions fail to send emails as well.

    Interestingly, everything works without any issues when using the WP Mail SMTP plugin with the exact same SMTP credentials and identical configuration.

    Could you please investigate what is causing this issue?

Viewing 2 replies - 1 through 2 (of 2 total)
  • Thread Starter alexqbox

    (@alexqbox)

    5 days, 7 hours ago

    Please see the attached screenshot.

    Plugin Support Ariful Islam

    (@arifulislam1)

    5 days, 1 hour ago

    Hi @alexqbox ,

    Apologies for the delayed reply. Thanks for sharing the screenshot.

    The browser console error is only a side effect of the real problem: the FluentSMTP test-email AJAX request is returning an HTTP 500 from wp-admin/admin-ajax.php.

    From our side, expected Outlook / Office 365 mailer errors should normally come back as a JSON response, so a raw 500 usually means one of these is happening before FluentSMTP can return its normal error message:

    1. a PHP fatal error on the site
    2. a plugin/theme conflict during the wp_mail() request
    3. a server-level security rule such as ModSecurity/WAF blocking the request

    Could you please do the following and share the result?

    • Enable WordPress debug logging, reproduce the issue once, and send us the exact lines written to /wp-content/debug.log at the time of the failed test.
    • If debug.log stays empty, please ask your host to check the server error log / ModSecurity log for that same request.
    • Please also confirm whether the site is multilingual (WPML/Polylang or language-prefixed URLs). If yes, that is especially relevant for Microsoft 365 because Microsoft requires the redirect URI to match exactly, and multilingual callback URLs are a known source of Outlook authorization issues.

    As an Office 365 sanity check, please also verify:

    • the token was generated with the same mailbox that is used as the sender address
    • the mailbox has an active Microsoft 365 license
    • the Azure app has the required Microsoft Graph delegated permissions and admin consent

    Once you share the debug/server log entry, we can usually pinpoint the exact cause very quickly.

    Thank you

Viewing 2 replies - 1 through 2 (of 2 total)

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