Email Settings GuideQuick answer: incoming and outgoing both use mail.optimum.net. IMAP is port 993, POP is 995, SMTP is 465 or 587, all with SSL and authentication on. The one detail people miss: the username is your Optimum ID, the part before the @, not your full address. The password is your Optimum email password. The same settings cover optimum.net and optonline.net. If your address ends in suddenlink.net, mail apps no longer connect.
mail.optimum.net, so the username rule and app-access notes on this page reflect what actually signs in rather than the full-address guess most guides repeat.
See what changed →
What Changed Recently#
Email providers change login rules more often than server addresses. Optimum has folded in Suddenlink and tightened how outside apps reach its mail, so what works now depends partly on your address and your service. Here is where Optimum email stands in 2026.
Latest update
Suddenlink.net addresses lost mail-app access. After Suddenlink became Optimum, users report that Outlook, Apple Mail and the iPhone Mail app no longer connect to suddenlink.net mailboxes. Those addresses are webmail or Optimum app only now. The optimum.net and optonline.net settings on this page still work.
Earlier change
The username is the Optimum ID, not the full address. Optimum's own guidance sets the username to the part before the @, for example jsmith rather than jsmith@optimum.net. Entering the full address is the most common reason a correct password still fails. See the rule.
Earlier change
Optimum email is tied to your service. The mailbox lives on while your Optimum account is active. Cancel your service and it keeps working for a while, then closes, with no guaranteed retention. Back up before you leave.
mail.optimum.net with your Optimum ID as the username and mail apps work. For suddenlink.net, use webmail or the Optimum app.
Before You Begin#
Two things sink most Optimum setups before the servers even matter. Sort both first.
1. Use your Optimum ID as the username
Optimum wants the username to be your Optimum ID, the portion left of the @, not the whole address. Typing the full address is the top reason a correct password is rejected. If your client insists on an address, try the full one as a fallback.
Where: The username rule below →
2. Check your address still connects
A suddenlink.net address no longer works in mail apps. Any Optimum mailbox also closes some time after you cancel service. Confirm your address type and that your service is active before troubleshooting settings.
Where: Will it work in your app? →
About Optimum Email#
Optimum is the cable and internet provider run by Altice USA, mainly in the New York area and parts of the South. Its email covers the optimum.net and optonline.net addresses.
Optonline.net is the older Optimum Online domain. Both it and optimum.net use the same servers. Suddenlink joined Optimum in 2022, but suddenlink.net mail has since lost third-party app access. The detail that trips up most setups is the username: Optimum wants your Optimum ID, the part before the @, where nearly every other provider wants the full address.
| Service Name | Optimum Email |
| Owned By | Altice USA |
| Email Domains | optimum.net, optonline.net |
| Username | Your Optimum ID, the part before the @ |
| Webmail URL | webmail.optimum.net |
| Servers | mail.optimum.net for IMAP, POP and SMTP |
| App Password Needed | No, your Optimum email password |
| Mail Apps | optimum.net and optonline.net only, not suddenlink.net |
@optimum.net and @optonline.net use mail.optimum.net. Only your Optimum ID changes, never the server.
Optimum Webmail Login#
You can always read Optimum mail in a browser. For suddenlink.net addresses it is the only option. The official pages are:
Webmail
webmail.optimum.net (webmail)
Account Security
optimum.net (account and password)
Forgot Email Password
Will Optimum Email Work in Your App?#
Before you enter a single server value, two Optimum rules decide whether a mail app can connect at all: which domain your address uses, plus whether your service is still active.
Your mailbox is tied to active service
Optimum email lives alongside your Optimum account. It does not vanish the moment you cancel, but it is not permanent either.
Leaving Optimum or worried about losing years of mail? Back the mailbox up first, then it is yours to keep.
Optimum IMAP Settings#
IMAP is the right incoming choice for most people, since it keeps mail on Optimum's server so every device shows the same inbox. Watch the username field:
| IMAP Server | mail.optimum.net | |
| Port | 993 | |
| Encryption | SSL/TLS (required) | |
| Username | Your Optimum ID, the part before the @, not the full address | |
| Password | Your Optimum email password | |
| Authentication | Required |
Optimum POP3 Settings#
POP3 downloads mail to one device, useful for a local copy on a single computer. Same server and same Optimum ID username. Not sure which to pick? See the comparison below.
| POP3 Server | mail.optimum.net | |
| Port | 995 | |
| Encryption | SSL/TLS (required) | |
| Username | Your Optimum ID, the part before the @ | |
| Password | Your Optimum email password |
Optimum SMTP Settings#
SMTP handles outgoing mail on the same host, with authentication on. If you can read but not send, this is almost always why:
| SMTP Server | mail.optimum.net | |
| Port (SSL) | 465 | |
| Port (STARTTLS) | 587 | |
| Encryption | SSL or STARTTLS (required) | |
| Username | Your Optimum ID, the part before the @ | |
| Password | Same as incoming mail | |
| Authentication | Required. Tick "My outgoing server requires authentication" and reuse the incoming login. Optimum's own guide calls this out. Skipping it is the top sending failure. |
Check Optimum IMAP Settings Online#
You don't need to download anything to check Optimum IMAP settings online. This page is the lookup, with every value verified and copyable. A domain check confirms an Optimum address, but remember the username is your Optimum ID, not the address itself. Type your address for a quick check:
Does my email address use these settings?
Runs in your browser only. Your address is never sent anywhere or stored.
Want to verify the account itself first? Sign in at Optimum webmail. A working webmail login proves the mailbox and password are fine, so an app failure points to the username being the full address instead of your Optimum ID. It can also be a suddenlink.net address that apps no longer accept.
Look Up IMAP Settings for Any Email Domain#
This page covers Optimum. For any other address, including a business domain on a different host, our free lookup database imapsettings.com returns the incoming and outgoing servers for any domain in one step.
imapsettings.com
Complete email settings database, by Univik
Enter any email address and get the incoming and outgoing server settings for that domain in 1 step:
Your address is used only to find the settings for that domain. Nothing is stored or shared.
The Optimum ID Username Rule#
This is the single biggest Optimum gotcha. The username is not your email address. It is your Optimum ID, the part before the @. Here is the difference:
| Field | What to enter | Do not enter |
|---|---|---|
| Username | jsmith (your Optimum ID) | jsmith@optimum.net |
| Email address | jsmith@optimum.net (the full address) | jsmith alone |
| Password | Your Optimum email password | Your TV or billing PIN |
| If sign-in still fails | Try the full address as username | Do not add extra spaces |
If You Forgot Your Optimum Email Password
- Go to webmail.optimum.net and choose the Forgot Email Password link.
- Confirm your Optimum ID and pass the identity check.
- Set a new email password, separate from your TV or billing PIN.
- Update it in your mail app for both incoming and outgoing, with your Optimum ID as the username.
Set Up Optimum in Email Clients#
The server is mail.optimum.net everywhere. The one thing to get right in every app is the username: your Optimum ID, not the full address. Jump to your app:
Outlook (Windows and Mac)
- Open Outlook → File → Add Account, open Advanced options and tick "Let me set up my account manually".
- Choose IMAP and enter
mail.optimum.netport993SSL incoming andmail.optimum.netport465SSL outgoing. - Set the username to your Optimum ID, the part before the @, with your Optimum email password.
- Open More Settings → Outgoing Server and tick "requires authentication".
- Finish and send yourself a test to confirm both directions work.
Apple Mail (macOS)
- Open Mail → Settings → Accounts → Add Account → Other Mail Account.
- Enter your name, full Optimum address and email password, then continue.
- When asked for servers, use
mail.optimum.netfor both incoming and outgoing. - Set the username to your Optimum ID, not the full address, on both servers, SSL on.
- Enable Mail and finish.
iPhone and iPad
- Open Settings → Apps → Mail → Mail Accounts → Add Account → Other.
- Tap Add Mail Account and enter your name, full Optimum address and email password.
- Keep IMAP selected and enter
mail.optimum.netfor both incoming and outgoing. - Set the username to your Optimum ID, the part before the @, in both host fields.
- Tap Save and wait for iOS to verify.
Android
- Open your mail app (Gmail app, Samsung Email or another) → Add account → Other or IMAP.
- Enter your full Optimum address and email password, then pick Manual setup.
- Enter the servers:
mail.optimum.net993 SSL incoming,mail.optimum.net465 SSL outgoing. - Set the username to your Optimum ID, not the full address.
- Finish setup and pull down to sync your inbox.
Thunderbird
- Open Thunderbird → Account Settings → Account Actions → Add Mail Account.
- Enter your name, full Optimum address and email password, then select Continue.
- Thunderbird may detect Optimum. Confirm IMAP and the server
mail.optimum.net. - Choose Configure manually and set the username to your Optimum ID, not the full address.
- Select Done. Folders sync on first open.
Optimum Webmail Settings#
Server settings connect your apps. These control how the mailbox behaves and live in Optimum webmail under Settings.
Signature
Settings → Signature. A signature set here shows in Optimum webmail only. Outlook and phone apps keep their own.
Vacation Auto Reply
Settings → Auto Reply. Set start and end dates so it turns off by itself. Optimum sends it from the server, so it runs with your computer off.
Filters and Folders
Settings → Filter Rules. Rules made here run on Optimum's server, so mail is sorted before any device syncs. A rule inside a desktop client only runs while that app is open.
Spam and Blocked Senders
Settings → Blocked Senders. Add addresses or domains to the block list. Blocked mail is sent to the spam folder.
Optimum POP3 vs IMAP#
The usual trade-off, against Optimum's server.
| Feature | IMAP | POP3 |
|---|---|---|
| Where mail lives | On the Optimum server | Downloaded to 1 device |
| Multiple devices | ✅ Everything stays in sync | ❌ Each device sees different mail |
| Sent and deleted mail | ✅ Synced everywhere | ⚠️ Stays only on that device |
| Offline reading | ⚠️ Cached mail only | ✅ Full local copy |
| Server storage used | Yes, counts against your quota | Can be freed after download |
| Best for | Phone + computer, everyday use | Single PC, local archives |
Optimum Sending and Storage Limits#
Optimum caps outgoing mail to deter spam. Hitting a limit pauses sending for a while. The rough shape, since Optimum does not publish exact figures:
| Mail apps | optimum.net and optonline.net only, not suddenlink.net |
| Daily sending | Capped to deter spam, ample for normal personal use |
| Attachment size limit | Around 20 to 25 MB to send |
| Mailbox storage | Generous for personal mail |
| What happens at the limit | Sending pauses, then resumes once the window resets |
Optimum Email Not Working#
Find the exact error your email app shows, then apply the fix:
| Error you see | What it means | Fix |
|---|---|---|
| Username or password incorrect | You entered the full address as the username | Use your Optimum ID, the part before the @, not the whole address. This is the most common cause. |
| Suddenlink account will not connect | suddenlink.net lost mail-app access | Those addresses are webmail or Optimum app only now. There is no server fix. |
| Cannot connect to server | Wrong port or SSL off | Use mail.optimum.net 993 SSL in and 465 SSL out. Avoid the legacy 143 and 110 ports. |
| Mail receives but will not send | SMTP authentication is off | Tick "outgoing server requires authentication" and reuse the incoming login with your Optimum ID. |
| Mail stopped after cancelling service | The mailbox closed once service ended | Optimum email is tied to active service. There is no fix after closure, so back up beforehand next time. |
Reader Reported Fixes
Two fixes that come up again and again in Optimum setups, beyond the error table above.
Fix the username before anything else. If a correct password keeps bouncing on an optimum.net or optonline.net account, change the username from your full address to just your Optimum ID, the part before the @. Most "Optimum will not connect" cases end here.
Confirm the address type when apps suddenly stop. A suddenlink.net address that once worked in Outlook or on an iPhone will no longer connect, since Optimum ended third-party access for those mailboxes. Switch to webmail or move the mail to a Gmail or Microsoft 365 account you fully control.
Suddenlink History and Leaving Optimum#
Came in from Suddenlink? Suddenlink joined Optimum in 2022, but suddenlink.net mailboxes have since lost third-party app access. If you still need that mail in an app, move it out while you can still reach it in webmail.
Leaving Optimum for another provider? Your optimum.net or optonline.net mailbox closes some time after your service ends, with no guaranteed retention. Back it up first so nothing is lost.
Moving your mail to a new account? The Univik Email Migration Tool copies every folder over IMAP into Gmail, Microsoft 365 or another account, using the Optimum settings on this page with your Optimum ID as the username.
Setting an Optimum address up next to another provider? Our email settings index has the servers for most hosts.
Rather not do it yourself? Our Email Migration Services team plans and runs the whole transfer and verifies every folder arrived.
Use These Settings in Univik Email Backup#
The IMAP settings above let you download a complete Optimum mailbox to your computer. Univik Email Backup saves everything as PST, MBOX, EML or PDF files you keep, which matters because an Optimum mailbox closes some time after you cancel service.
- Download Univik Email Backup and install it on Windows.
- Choose Optimum or IMAP as the source.
- Enter the server
mail.optimum.neton port 993 with SSL, from the IMAP table above. - Sign in with your Optimum ID and email password, not the full address. Include every folder.
- Pick PST, MBOX, EML or PDF and a folder, then start. Large mailboxes download in the background.
Univik Tools That Use These Settings#
Many people land here while migrating or archiving a mailbox. All 3 tools use the same IMAP settings from this page:
Email Backup
Save a complete Optimum mailbox to PST, MBOX, EML or PDF before cancelling service closes it.
Email Backup Tool →
Email Migration Tool
Copy every folder from Optimum straight into Gmail, Microsoft 365 or another account over IMAP.
Email Migration Tool →
Email Converter Tool
Already exported MBOX, EML or PST files? Convert them to whatever format your next email app opens.
Email Converter Tool →Prefer to hand the whole migration to experts?
If the username rule and the leaving-Optimum deadline feel like too much, you don't have to sort it out alone. Univik's migration team handles the complete project: planning, transfer, verification and a report showing every folder made it. Since 2013, for single mailboxes up to full company moves.
Email Settings Glossary#
IMAP
Internet Message Access Protocol, on port 993. Mail stays on Optimum's server so every device shows the same inbox. Uses mail.optimum.net.
POP3
Post Office Protocol version 3, on port 995. Downloads mail to one device. Also uses mail.optimum.net on Optimum.
SMTP
Simple Mail Transfer Protocol, the sending half. Optimum uses mail.optimum.net on port 465 or 587, always with authentication on.
SSL / TLS / STARTTLS
Encryption for the connection. SSL/TLS covers ports 993, 995 and 465 on Optimum. STARTTLS upgrades a plain connection on 587. The legacy 143 and 110 ports are not recommended.
Optimum ID
Your Optimum ID is the part of your address before the @. Optimum uses it as the username in mail apps, where other providers use the full address.
optonline.net
The older Optimum Online email domain. An optonline.net address uses the same mail.optimum.net servers as optimum.net.
How We Verify These Settings#
Univik has built email backup, migration and converter software since 2013. Optimum mailboxes pass through our tools regularly. That is how we can flag the two things generic guides get wrong on Optimum: the username is your Optimum ID, not the full address, plus suddenlink.net no longer works in apps.
Every value here is confirmed with three checks: a live IMAP and SMTP connection from Univik Email Backup, a comparison with Optimum's own faq.optimum.net pages and a real sign-in using an Optimum ID and email password. We re-check after any Optimum announcement and at least once a quarter.
Found a value that no longer matches what Optimum shows you? Tell us and we will retest and update the page, with the change logged in what changed recently.
Help & Support
Frequently Asked Questions
Use mail.optimum.net on port 993 with SSL. The username is your Optimum ID, the part before the @, not the full address, with your Optimum email password. The same settings cover optimum.net and optonline.net. The full table is in the IMAP settings section.
Almost always because the username is set to your full address. Optimum wants your Optimum ID, the part before the @, for example jsmith rather than jsmith@optimum.net. Fix the username and a correct password goes through.
IMAP suits nearly everyone because it mirrors your inbox across phone, computer and webmail. POP3 suits a single-computer download. For a lasting copy before leaving Optimum, a backup beats both. Full comparison here.
The outgoing server is mail.optimum.net on port 465 with SSL, using 587 with STARTTLS as an alternate. Turn on "my outgoing server requires authentication" and use your Optimum ID as the username, since that is the top reason Optimum sends nothing. Full details are in the SMTP settings section.
Not reliably. The mailbox is tied to your Optimum service and closes some time after you cancel, with no guaranteed retention. It may keep working for a while, but do not count on it. Back up and move your mail before your service ends. See how access works.
After Suddenlink joined Optimum, suddenlink.net mailboxes lost third-party app access. They are webmail or Optimum app only now. No server settings will change that. To use the mail in an app again, move it to an account you control. More on app access.
Yes. Both use mail.optimum.net for IMAP, POP and SMTP, with your Optimum ID as the username. Only the domain in your address differs. To keep a permanent copy of either mailbox, see how to back it up.
The likely Optimum causes: your service was cancelled and the mailbox closed, the address is a suddenlink.net one that apps no longer accept or a client update reset the username to your full address. Check app access and the username rule, then what changed recently.
An email migration tool copies mail between accounts over IMAP. Use the Optimum IMAP settings with your Optimum ID as the username on one side and the destination account on the other. Do this while your service is active, since the mailbox closes after you cancel. Every folder stays intact.
With several Optimum mailboxes to move before leaving, our managed email migration service can run the whole project for you.
Other Email Provider Settings
Summary: Optimum Settings at a Glance
- IMAP: mail.optimum.net, port 993, SSL
- POP3: mail.optimum.net, port 995, SSL
- SMTP: mail.optimum.net, port 465 or 587
- Username is your Optimum ID, the part before the @
- Same servers for optimum.net and optonline.net
- suddenlink.net no longer works in mail apps
- Mailbox is tied to active service
- Back up before you cancel Optimum