Network troubleshooting technician providing live chat help

Joe B.

Reviewed for technical accuracy

Specialities: Home networking & Wi-Fi, IMAP/SMTP email issues, Outlook & Apple Mail, DNS & ports, ISP/router firewall and content filtering

Fix IMAP/SMTP not working on Wi-Fi — mail server not responding, cannot send or receive email

Technician avatar Technician
Hi! We’ll get your IMAP/SMTP not working on Wi-Fi problem sorted so email sends and receives normally again. I just need a quick picture of your setup.

Which email provider are you using (Gmail, Outlook/Hotmail, Yahoo, your ISP, company email, etc.) and which apps/devices show the error — Outlook on Windows, Apple Mail on Mac, iPhone/iPad Mail, Android mail app? Do you see messages like “Cannot get mail – the mail server is not responding”, “Outlook cannot connect to the IMAP server”, or “SMTP server not available on Wi-Fi”?

Also, does email fail on every Wi-Fi network, or only on your home Wi-Fi? For example, does it work over mobile data or a phone hotspot but not on your normal router? That tells us whether this is a Wi-Fi / router issue, an IMAP/SMTP settings issue, or something on a specific device.
Customer
It seems to be only on our home Wi-Fi. I use Outlook on a Windows laptop and the built-in Mail app on my iPhone. Both of them started having issues at the same time.

On the laptop I get “Outlook cannot connect to the incoming (IMAP) server” and it won’t send either — the SMTP test fails. On the iPhone it says “Cannot Get Mail – the mail server is not responding”. If I turn off Wi-Fi and use mobile data, both devices work. Webmail in the browser also works fine on Wi-Fi.
Technician avatar Technician
That’s really useful info — classic case of email not working on Wi-Fi but working on mobile data.

When IMAP or SMTP won’t connect on Wi-Fi but web browsing and webmail work, it usually points to one (or a mix) of these:

• Your router/ISP is blocking or filtering the mail ports (IMAP 993/143, SMTP 465/587/25), so apps can’t reach the mail server over Wi-Fi.
• The email account in Outlook/iPhone is still using old, insecure ports or no encryption (like SMTP on port 25), which many providers or ISPs now block on home networks.
• A security tool — router firewall, DNS/content filter, or antivirus “email scanning” — is breaking the connection to the IMAP/SMTP server while letting normal web traffic through.
• Less commonly, the account needs updated authentication (app password / OAuth) so the IMAP/SMTP login works on all networks, not just mobile data.

We’ll first confirm your Wi-Fi connection itself is stable, then check whether the problem follows the Wi-Fi network or the device, and finally fix your IMAP/SMTP settings and ports so mail syncs normally.
Customer
Internet in general is fine. On Wi-Fi I can browse websites, stream video, use Teams, everything. It’s literally only email apps that act up. I tried rebooting the router and forgetting/re-joining Wi-Fi on my iPhone, no change. On my phone if I switch to 5G it starts loading mail right away. Same if I tether the laptop through the phone — Outlook works over the hotspot.
Technician avatar Technician
Perfect — that test tells us a lot. Your email account and password are fine, because everything works on mobile data and on the hotspot. The problem is specifically IMAP/SMTP over your home Wi-Fi network.

Let’s do a quick, safe round of checks:

Step A — Confirm Wi-Fi vs device issue
1) While on home Wi-Fi, open a browser and go to your mail provider’s webmail (Outlook.com, Gmail.com, etc.). Since that loads, we already know basic internet and DNS are okay, but it’s still good to confirm.
2) Temporarily turn off any VPN on the laptop and phone. VPNs sometimes break connections to mail servers or force different ports.
3) Check whether you’re on a guest Wi-Fi or restricted SSID from your router. Guest networks often block outgoing SMTP or IMAP ports so only web browsing works.
4) If your router has parental controls, “safe browsing”, or security features from the ISP app, note that those can block mail traffic (IMAP/SMTP) while leaving HTTPS sites alone.

After that, we’ll open Outlook’s and the iPhone’s IMAP/SMTP settings to see which servers, ports, and encryption they’re trying to use over Wi-Fi.
Customer
I’m on the main home Wi-Fi, not the guest network. I don’t use a VPN on either device. We do have some built-in “security” in the ISP router app, but it’s just the default setting and I never changed it.

I checked Outlook’s account settings: incoming is set to imap.mail.xxx.com on port 143 without SSL, and outgoing SMTP is smtp.mail.xxx.com on port 25. On the iPhone it’s basically the same values that were auto-filled years ago. Could that be the problem?
Technician avatar Technician
Yes — that’s the heart of it.

Most providers today expect encrypted IMAP and SMTP, and many ISPs now block unencrypted SMTP on port 25 over Wi-Fi to cut down spam. That’s exactly how you end up with IMAP/SMTP not working on Wi-Fi while webmail and mobile data still work.

Step B — Fix IMAP and SMTP server settings
In Outlook on the laptop:
• Change IMAP to use SSL/TLS on port 993 (or the secure IMAP port your provider lists).
• Change SMTP to use STARTTLS on port 587 or SSL/TLS on port 465 — again matching your provider’s documentation.
• Make sure “My outgoing server (SMTP) requires authentication” is turned on and set to “Use same settings as my incoming mail server”.

On the iPhone Mail account:
• In Incoming Mail Server, turn on Use SSL and set the correct IMAP port (usually 993).
• In Outgoing Mail Server (SMTP), tap the primary server and set Use SSL or TLS with the proper port (465 or 587) and your full email address + password.

After saving, back out of settings, fully close the mail apps, then reopen them on Wi-Fi and try a send/receive. Let me know if IMAP or SMTP still fails on Wi-Fi after those changes.
Customer
I updated the ports and turned on SSL like you said. Outlook now shows IMAP on 993 with SSL and SMTP on 587 with STARTTLS and authentication. On the laptop, the test message finally went through and it’s syncing again on Wi-Fi.

The iPhone is better but still a bit weird. It will sometimes say “Cannot Get Mail” once, and then after a while the inbox refreshes. Sending from the phone on Wi-Fi sometimes hangs for a long time.
Technician avatar Technician
Great — that confirms your home Wi-Fi and router can handle secure IMAP/SMTP just fine, and that the new ports are working. Now we’ll clean up the phone so it’s just as reliable.

Step C — Fix “Cannot Get Mail – mail server not responding” on iPhone/Android
1) First, make sure the iPhone is using the same updated IMAP/SMTP hostnames, ports, and SSL/TLS that we set on the laptop.
2) If your provider uses two-factor authentication (Microsoft 365, Gmail, some ISPs), the phone may need either an app password or to sign in via the provider’s login page instead of just typing the password once.
3) A very reliable fix is to remove the email account from the phone completely, restart the phone, then add the account back using the built-in “Outlook/Exchange”, “Gmail” or “Microsoft/Google” option so it auto-configures modern IMAP/SMTP settings.
4) After re-adding, test on mobile data and then again on your Wi-Fi. The goal is that the mail app connects to the same secure IMAP and SMTP configuration we know works on your laptop.

If email works perfectly on mobile data but still randomly stalls only on home Wi-Fi after this, we’ll do one final pass on your router’s DNS and security filters.
Customer
I deleted the account from my iPhone and added it again using the Outlook/Exchange option. It walked me through a sign-in page, so I guess it did the OAuth thing. Now it syncs much faster and I can send from the phone on mobile data without errors.

On Wi-Fi it mostly works, but every now and then it still pops “mail server not responding” for a second before succeeding. My partner’s Android phone with the same account also had some time-outs on Wi-Fi earlier.
Technician avatar Technician
Since both phones see IMAP/SMTP time-outs on Wi-Fi, this last bit is likely the network itself — usually DNS or a “smart security” feature in the router/ISP app.

Step D — Tune Wi-Fi, DNS and security so email is stable
• In your router or ISP app, look for any setting named Safe browsing, Web shield, Email protection, Child protection, or Content filter. Try temporarily turning those off and see if the “IMAP/SMTP not responding on Wi-Fi” error disappears.
• On one phone, set custom DNS servers on the Wi-Fi network — for example, 8.8.8.8 and 1.1.1.1 — then reconnect and test mail. Flaky ISP DNS often causes “server not responding” for IMAP/SMTP hostnames.
• Make sure you’re connecting to the main home SSID, not a heavily restricted guest Wi-Fi. Guest networks sometimes block all outgoing mail ports by design.
• If you run security software on the laptop (antivirus with email scanning), disable just the email-scanning module as a test. Some products break TLS connections to IMAP/SMTP servers.

Once these are tuned, testing the same account on multiple devices (Outlook on Windows, iPhone Mail, Android) over Wi-Fi should show consistent, stable IMAP and SMTP connections without random time-outs.
Customer
That was it. In the ISP router app there was an option called “Advanced security / email spam protection” that was apparently inspecting SMTP traffic. I turned that off and also set the router’s DNS to use Google’s servers.

Since then, none of the devices have shown any IMAP or SMTP errors on Wi-Fi. Outlook syncs fine, my iPhone isn’t throwing “Cannot Get Mail”, and my partner’s Android mail is happy too.
Technician avatar Technician
Excellent — that lines up perfectly: the “smart” security was interfering with encrypted IMAP/SMTP traffic over Wi-Fi.

To avoid this “IMAP/SMTP not working on Wi-Fi” situation coming back every few months, a few best practices:

• Keep all accounts configured with your provider’s recommended IMAP and SMTP servers, ports, and SSL/TLS settings — avoid old port-25/no-encryption setups even if they still work on some networks.
• For Microsoft 365, Outlook.com, Gmail and similar, prefer adding accounts via the built-in Microsoft/Google/OAuth wizards so app passwords and modern authentication stay in sync.
• In your router/ISP app, leave reasonable web protection on, but avoid features that specifically say they inspect or block email/SMTP/IMAP unless you know they’re compatible with your provider.
• If your ISP offers a separate guest Wi-Fi, don’t put your main laptops/phones on that network — those SSIDs often block outgoing mail entirely.

With that in place, your email apps should keep working on Wi-Fi, and if something breaks later you’ll know to check ports, encryption, and router filters first.
Customer
Got it. I saved screenshots of the working IMAP/SMTP settings and left the router security on a lighter mode. Everything has been stable for the last hour — no “mail server not responding” pop-ups at all. Thanks for walking me through all of this.
Technician avatar Technician
You’re very welcome — happy to hear everything’s stable again.

Quick recap: When IMAP/SMTP is not working on Wi-Fi but webmail and mobile data are fine, the usual fix is to move all apps to the provider’s secure IMAP (typically 993) and SMTP (587/465 with TLS) settings, enable SMTP authentication, and then turn off or tune any router/ISP feature that inspects or blocks mail ports. Re-adding the account on phones with modern authentication clears out old, half-working profiles.

If you ever see “Cannot Get Mail – the connection to the server failed” or “Outlook cannot connect to the IMAP/SMTP server” again, you can open a chat with an expert and we’ll trace it with you step by step.
Customer
Sounds good. I’ll definitely reach out if email or Wi-Fi act up again. Really appreciate the detailed explanations.
Technician avatar Technician
Any time! If a friend complains that email only works on mobile data, their IMAP server is not responding on Wi-Fi, or they can’t send because the SMTP server keeps timing out, you can share this checklist — or just have them start a chat with an expert and we’ll take care of the IMAP/SMTP and Wi-Fi troubleshooting for them.

Quick answer: the accepted fix

Accepted fix when IMAP/SMTP is not working on Wi-Fi: confirm the Wi-Fi connection is stable and webmail works, then switch all apps to your provider’s secure IMAP (usually 993) and SMTP (587 or 465 with TLS/SSL) settings with SMTP authentication turned on. Finally, disable or tune any router/ISP security feature that blocks mail ports so “mail server not responding” and “cannot send email on Wi-Fi” errors clear on every device.

Why IMAP/SMTP stop working on Wi-Fi (ports, SSL/TLS, router filters)

Most IMAP/SMTP not working on Wi-Fi issues are not caused by the mailbox itself, but by how your apps and Wi-Fi network talk to the mail servers. If Outlook, Apple Mail or your phone’s mail app uses old settings — for example, IMAP on port 143 without encryption or SMTP on port 25 with no authentication — your home router or ISP may quietly block that traffic while still allowing normal web browsing.

Another common cause is aggressive router security, parental controls, or DNS filtering that inspects connections on ports 993, 465, 587, and marks them as suspicious. That’s when you see “incoming mail server not responding” or “SMTP server connection failed” only on Wi-Fi, but everything works on a mobile hotspot. Using the correct IMAP/SMTP ports with SSL/TLS and relaxing just the email-related filters usually fixes it for good.

How to tell if it’s Wi-Fi, your mail app, or the email provider

To quickly narrow down an email not working on Wi-Fi problem, separate the path into device → Wi-Fi/router → email provider:

First, test webmail in a browser while on the same Wi-Fi. If webmail loads and sends, your internet connection and account are fine. Next, try the same mail account on a different network, like mobile data or a phone hotspot. If IMAP and SMTP only fail on your home Wi-Fi, the issue is ports, DNS, or filters on that network. If they fail everywhere, focus on the mail client’s server names, ports, SSL/TLS options, authentication, and app passwords, or check if the provider is having an outage.

IMAP/SMTP not working on Wi-Fi — quick troubleshooting tips

Use secure ports, correct server settings, and Wi-Fi that doesn’t block mail traffic.

Fast path: confirm other websites and webmail work on Wi-Fi → compare behavior on mobile data vs home Wi-Fi → update each device to use your provider’s documented IMAP and SMTP server names, ports (993/587/465), and SSL/TLS → turn on SMTP authentication → temporarily disable router “email protection” or content filters to see if they’re blocking mail ports. Once those pieces match, “Cannot Get Mail” and SMTP connection errors on Wi-Fi usually disappear.

Disclaimer: This information is AI-generated and intended for general guidance only. For advice specific to your email provider, Wi-Fi router, and devices, please consult a verified expert on Whizz-Tech before making decisions.

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FAQ

Why do IMAP/SMTP stop working only on my Wi-Fi network?

If IMAP/SMTP only fail on Wi-Fi but work on mobile data, your router or ISP is usually blocking or filtering mail ports, or your mail app is using outdated settings. Common causes are SMTP still on port 25 without encryption, IMAP on port 143 without SSL/TLS, or “advanced security” features that inspect mail traffic. Updating to your provider’s secure IMAP/SMTP ports and adjusting router filters usually fixes it.

How do I fix “Cannot Get Mail – the mail server is not responding”?

First, make sure webmail and other sites work on Wi-Fi. Then check your mail app’s server settings: use the correct IMAP hostname, enable SSL/TLS, and use the right port (normally 993). For SMTP, use port 587 or 465 with authentication. If you changed your password or turned on two-factor authentication, you may need to remove and re-add the account or use an app password so the IMAP and SMTP servers accept the connection.

Which ports and encryption should IMAP and SMTP use?

Most providers recommend IMAP over SSL/TLS on port 993 for incoming mail and SMTP with STARTTLS on port 587 or SMTP over SSL/TLS on port 465 for outgoing mail. Your email address, full username, and password are used for authentication. Check your provider’s documentation, then match those values exactly in Outlook, Apple Mail, or your phone mail app.

When should I contact my email provider or ISP?

If your devices are using the correct IMAP/SMTP settings, mail still fails on every network, or only your address is affected while others work, contact your email provider to check for account locks, password issues, or service outages. If email works on mobile data but fails on every device connected to your home Wi-Fi, ask your ISP whether they block certain ports or have a security feature that might be interfering with encrypted IMAP/SMTP connections.

Sources

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