✉️ How to Fix Common Email Problems
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How to Fix Common Email Problems

Category: Email · Audience: Client & Internal · Updated: March 2026

Quick fixes for the most common email issues — emails not sending, not receiving, attachments failing, and more.

"I Can't Send Emails"

Check 1 — Is there an error message?

Look at the Outbox folder in Outlook. If emails are stuck there, Outlook will usually show an error in the bottom status bar. Common messages include "disconnected", "need password", or "server unavailable".

Check 2 — Is Outlook connected?

Look at the bottom-right of the Outlook window. If it says Disconnected or Trying to connect, check your internet connection first. If the internet is working, restart Outlook.

Check 3 — Is the attachment too large?

Microsoft 365 limits email attachments to 25 MB. If your file is larger, use OneDrive: upload the file to OneDrive and share a link in the email instead of attaching the file directly.

Check 4 — Are you getting a bounce-back?

If you receive an automated reply saying the email couldn't be delivered, read the error message carefully. Common causes include: the recipient's address is wrong, their mailbox is full, or their server is rejecting your email.

Tip: If a bounce-back mentions "SPF", "DKIM", or "DMARC", it's a sender authentication issue. Contact ATS Systems — this may need a DNS configuration fix.

"I'm Not Receiving Emails"

Check 1 — Check Junk/Spam folder

Emails sometimes end up in the Junk Email folder. If you find a legitimate email there, right-click it and select Not junk to train the filter.

Check 2 — Check Focused vs Other inbox

If you're using Focused Inbox in Outlook, the email may be in the Other tab. Click the Other tab to check.

Check 3 — Check Quarantine

If your organisation uses email filtering (e.g. Avanan, Microsoft Defender), the email may have been quarantined. Check your quarantine notifications or contact ATS Systems to release it.

Check 4 — Ask the sender to check their end

Ask the sender if they received a bounce-back. If they did, the issue is on their side or in transit — not with your mailbox.

"I Can't Open an Attachment"

  • PDF files — Make sure you have a PDF reader installed (Adobe Acrobat Reader or the built-in browser PDF viewer).
  • ZIP files — Windows can open ZIP files natively. Right-click → Extract All. If it's a password-protected ZIP, you'll need the password from the sender.
  • Blocked attachments — Outlook blocks certain file types (.exe, .bat, .js) for security. If you need the file, ask the sender to upload it to OneDrive or SharePoint and share a link instead.

"My Email Signature Is Missing or Broken"

Outlook signatures are stored locally on each device. If you set up a signature on your desktop, it won't automatically appear on your phone or the web.

  • Desktop: Go to File → Options → Mail → Signatures to create or edit.
  • Mobile: Go to Settings → [your account] → Signature.
  • Web: Go to outlook.office.com → Settings (gear icon) → View all Outlook settings → Mail → Compose and reply.

Good to know: If your organisation uses a company-wide email signature applied by a server rule, your local signature may appear duplicated. Contact ATS Systems if this happens.

"Someone Is Sending Emails from My Account"

If colleagues or contacts are receiving emails you didn't send:

  1. Change your password immediately.
  2. Check your Sent Items and Deleted Items for emails you didn't write.
  3. Check Inbox Rules — Attackers often create hidden rules that forward or delete emails. Go to Settings → Rules and remove anything suspicious.
  4. Call ATS Systems on 07 3523 3660 — We'll investigate the account, revoke attacker access, and check for further compromise.

🔒 Internal Note (Technicians)

For account compromise investigation:

  1. Check Entra ID → Sign-in logs for sign-ins from unfamiliar IPs or locations.
  2. Check Exchange Online → Inbox Rules via PowerShell: Get-InboxRule -Mailbox user@domain.com | Select Name, Description, Enabled, ForwardTo, RedirectTo
  3. Check Mail Flow → Message trace for unusual outbound volume.
  4. Revoke sessions: Entra ID → Users → select user → Revoke sessions.
  5. Reset password, reset MFA, remove suspicious Inbox Rules, and check for OAuth app consent grants under Enterprise applications → User consent.

Need help? Call 07 3523 3660 or submit a ticket at atssystems.com.au/support/ticket/