An "SMTP Error: Could not connect to SMTP host" or "Failed to connect to server" message almost always means one of three things: the port and encryption method don't match what the mail server expects, the mailbox credentials are wrong, or something on the sending end is blocking the connection outbound. Start by checking the port and encryption pairing, since that causes the majority of these errors.
Check the port and encryption pairing first
SMTP plugins like WP Mail SMTP or Fluent SMTP fail most often because the port number doesn't match the encryption type selected. For a Flashcloud-hosted mailbox, the correct combinations are:
mail.yourdomain.comon port465with SSL encryptionmail.yourdomain.comon port587with STARTTLS encryption
Mixing these up is the single most common cause of connection failures. Port 465 expects the connection to be encrypted from the first handshake (SSL). Port 587 expects the connection to start unencrypted and then upgrade to TLS partway through (STARTTLS). If your plugin is set to port 465 with STARTTLS, or port 587 with SSL, the SMTP host will refuse the connection or time out. Open your SMTP plugin's settings and confirm the host, port, and encryption method match one of the two pairings above exactly.
Also confirm the username is the full email address (you@yourdomain.com), not just the local part.
Confirm the mailbox actually exists and the password is current
If the port and encryption are correct and you're still getting an authentication failure rather than a connection timeout, the problem is usually the credentials, not the server. Check:
- The mailbox exists under Email Accounts in the portal for the domain you're sending from. A typo in the address, or sending from a domain that doesn't have a mailbox set up yet, will fail here.
- The password in your SMTP plugin matches the mailbox's current password. If you changed it recently in Email Accounts without updating the plugin, authentication will fail even though the mailbox itself is fine. For a similar troubleshooting pattern with stale credentials, see fixing WordPress database connection errors.
- You're not accidentally trying to send through a different domain's mailbox than the one WordPress is installed on. Cross-domain sending from a shared plan can work, but only if you use the full mailbox address and its own password, not the primary domain's.
If you're unsure of a mailbox's password, reset it from Email Accounts in the portal and update the SMTP plugin with the new one.
Rule out the plugin defaulting to PHP mail()
Some contact form and SMTP plugins silently fall back to PHP's built-in mail() function if the SMTP configuration test fails, instead of showing you a clear error immediately. This produces confusing symptoms: no connection error appears, but no mail arrives either, or it arrives inconsistently and lands in spam. If your plugin has a "send a test email" feature, use it after every settings change so you see the actual connection error rather than a silent fallback.
If the test email log shows a timeout rather than an authentication error, that points to something blocking the outbound connection rather than bad credentials, covered next.
Check for a firewall block on the sending side
A timeout (the connection hangs and eventually fails, rather than being rejected immediately) usually means a network-level block rather than a credentials problem. If you've confirmed the host, port, encryption, and credentials are all correct and you're still getting timeouts, open a ticket to have the outbound mail path checked.
If you changed PHP versions around when this started, roll back temporarily via the PHP Version tile to rule that out before assuming it's a firewall issue.
When to open a ticket
If you've verified the port/encryption pairing, confirmed the mailbox and password are correct, tested with a fresh test email, and you're still getting timeouts rather than authentication errors, open a ticket via Support → New ticket in the portal. Include the exact error text from your SMTP plugin's debug log and the port/encryption combination you're using.