Business Email Not Sending or Receiving: A Troubleshooting Guide

When business email stops, customers' quotes, bookings and invoices go nowhere, and often nobody notices for a day or two. The causes range from a full mailbox to a domain that quietly expired.

This guide is for email on your own domain (such as name@extrion.co.tz), whether it is hosted with your website on cPanel or with a provider such as Google Workspace or Microsoft 365. Work through it in order: the first checks catch most problems.

Symptoms

• You cannot send: the app shows an error, or messages stay in the outbox.
• You send, but a "delivery failed" message (a bounce) comes back.
• Messages you send land in recipients' spam folders.
• You receive nothing, or only from some senders.
• Email works on the computer but not on the phone, or the other way round.
• Webmail works, but your mail app keeps asking for the password.

Likely causes

1. Expired domain. If the domain lapses, its DNS stops working and so does email.
2. Wrong or missing MX records. The MX records tell the world which server receives your email. After a move between hosts, they often point to the old server.
3. Missing or broken SPF, DKIM or DMARC. Receiving servers use these to check that mail really comes from you. Without them, messages go to spam or are rejected.
4. Full mailbox. A mailbox over its quota rejects new mail.
5. Wrong app settings. Wrong server name, port or encryption, or an old saved password.
6. Blacklisting. Your sending server's IP address is on a spam blocklist, often because an account on it was hacked and sent spam.
7. Spam filtering. Mail is arriving, but into a junk folder.
8. Sending limits. Shared hosting limits how many emails an account can send per hour.

Safe checks you can do

1. Read the bounce message. It usually says exactly what is wrong. A code starting with 5 is a permanent failure, such as "mailbox full", "user unknown" or a rejection because of SPF or a blacklist. A code starting with 4 is temporary, so the server will retry.
2. Try webmail. Log in to webmail (in cPanel hosting, often at yourdomain/webmail). If webmail sends and receives, the server is fine and the problem is your app or device.
3. Check the domain's expiry date with your registrar, or with a WHOIS lookup.
4. Check the mailbox size. In cPanel, Email Accounts shows each mailbox's usage and quota.
5. Look in the spam or junk folder, both yours and the recipient's.
6. Send a test to a personal Gmail or Outlook address, and from it back to your business address.
7. Ask whether anything changed: a new website host, a new email provider, DNS changes, a changed password.

Warning If you see thousands of messages you did not send in your Sent folder or the mail queue, an account is probably compromised. Change that mailbox's password immediately, from a clean device, and tell your host.

Solutions

Renew an expired domain

If the domain has expired, renew it at once with your registrar. Email and website start working once DNS is restored, which can take a few hours. Registries have grace periods after expiry, but they are not unlimited and late recovery can cost more. Set the domain to auto-renew, and make sure the renewal reminders go to an address that is not on the same domain. See our domains page.

Check MX records

MX records should point to whoever hosts your mailboxes:

• cPanel hosting: usually your domain or mail.yourdomain, pointing to the hosting server.
• Google Workspace or Microsoft 365: the records those providers give you in their set-up instructions.

In cPanel, also check Email Routing. If your mail is hosted with Google or Microsoft but routing is set to Local Mail Exchanger, messages sent from your website or other accounts on the same server stay on the server and never reach the real mailboxes. Set it to Remote Mail Exchanger in that case.

Warning Changing MX records moves where new email is delivered. A mistake means mail goes to the wrong place or bounces. Note the current records before editing, and change them only if you know where your mailboxes are hosted.

Set up SPF, DKIM and DMARC

These three DNS records help receiving servers trust your mail. Google's email sender guidelines require all senders to Gmail to use SPF or DKIM, and bulk senders to use SPF, DKIM and DMARC.

• SPF lists the servers allowed to send for your domain. You must have only one SPF record. Two separate SPF records break both. If you send through your host and also through, for example, a newsletter service or Microsoft 365, combine them in one record.
• DKIM adds a digital signature to every message. In cPanel, the Email Deliverability page (under Email) shows whether SPF and DKIM are valid, and can generate a DKIM key and suggest a correct SPF record. cPanel's Email Deliverability documentation explains it. For Google or Microsoft mailboxes, follow their own DKIM instructions.
• DMARC tells receiving servers what to do with mail that fails SPF and DKIM checks, and where to send reports. Start with a monitoring policy (p=none) and a reporting address, then tighten to quarantine or reject once you are sure all your legitimate mail passes.

Plays from YouTube when you press play.

Free up a full mailbox

• Empty the Trash and Spam folders, and delete or archive large attachments.
• If your app uses POP3, set it to remove messages from the server after a few days, or switch to IMAP and archive old mail locally.
• Raise the quota in cPanel Email Accounts if your plan allows.

Use the right ports and SSL settings

Use these standard settings in desktop and phone mail apps:

• Outgoing (SMTP) authentication must be on, using the same email address and password.
• Avoid port 25 for sending from apps. Many internet providers block it.
• Use the server name your host gives you. In cPanel, Email Accounts > Connect Devices shows the exact settings, including the server name that matches the SSL certificate. Using a different name causes "cannot verify server identity" warnings.

Check blacklists

If bounces mention a block list or "poor reputation", look up your sending server's IP address on a blacklist checker such as MXToolbox. If it is listed:

• find and secure any compromised account first (strong new passwords, check phones and computers for malware);
• on shared hosting, contact your host. The IP address is shared and they handle delisting;
• request removal from each list only after the cause is fixed.

Reduce mail going to spam

• Set up SPF, DKIM and DMARC as above.
• Avoid sending bulk newsletters from your ordinary mailbox. Use a proper newsletter service, set up with your domain's records.
• Ask regular contacts to mark your messages as "not spam" and add you to their contacts.
• Do not use link shorteners or attachments people do not expect.

Fix phone mail apps

• After changing a mailbox password, update it on every device. A phone retrying an old password can trigger security blocks.
• Delete the account from the phone and add it again using manual IMAP settings from the table above, rather than letting the app guess.
• Make sure the phone's date and time are set automatically. A wrong clock breaks secure connections.
• Some mail apps check your mailbox through their own cloud servers rather than directly from the phone. If one app fails and another works, try the phone's built-in mail app to isolate the problem.

When to call a professional

Contact your host or IT provider if your domain's DNS is managed somewhere you cannot reach, you are moving between email providers, you suspect a hacked account, your server is blacklisted, or bounces mention errors you cannot interpret. Before calling, collect:

• The full bounce message, including the error code (forward it, do not just describe it).
• Your domain name and who hosts the email (cPanel, Google, Microsoft or other).
• Which mailboxes are affected, and whether webmail works.
• Screenshots of your app's server settings and any error.
• A screenshot of the Email Deliverability page, if you use cPanel.
• What changed recently.

Frequently asked questions

When to call Extrion

Extrion Tech hosts business email on cPanel, registers domains and can set up MX, SPF, DKIM and DMARC records correctly. See our hosting plans or contact us with your domain name and a copy of the bounce message.

This guide is general information to help you plan. Prices, product features and regulations change, so confirm the details for your own site before you buy.

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