Mac Mail Not Connecting to Server? How to Fix It (2026)

Short answer: When Mail says it can't connect to the server, check three things in order: that your internet works without a VPN or network filter in the way, that your provider isn't having an outage, and that the account's server settings and password in Mail are right. Mail's Connection Doctor (Window > Connection Doctor) shows which server fails. The error "Connections to host (null) on the default ports failed" usually means Mail has no server name to try, so fill in the Host Name or pick an outgoing server in Server Settings, or remove the account and add it back.

The steps are for macOS 27 and also work on macOS Tahoe 26, Sequoia 15 and Sonoma 14.

What Mail's connection errors mean

Mail's messages are terse, but each one points somewhere specific. These are the wordings Mail uses, with the server name in place of "server":

Message	What it usually means	Try first
Connections to host (null) on the default ports failed	Mail has no server name to connect to: the Host Name is blank, the outgoing server is set to None or was deleted, or the account's settings are damaged	Fill in the Host Name or choose an outgoing server in Server Settings; otherwise remove and re-add the account
The server "server" cannot be contacted on the default ports	Mail tried its usual ports and got no answer: the server name is wrong, the server is down, or something blocks the connection	Check the Host Name, the provider's status page and any VPN or firewall app
Connections to the server "server" on the default ports timed out	The connection started but got no reply in time, often a slow or filtered network	Try another network; turn off VPN or network filters
Mail was unable to connect to server "server" using SSL on the default ports	The secure connection failed: wrong port or security setting, or a certificate problem	Turn on Automatically manage connection settings, or enter your provider's port and TLS/SSL setting
Cannot send message using the server "server"	The outgoing (SMTP) server rejected the message or the sign-in	See Mac Mail not sending emails

"Default ports" means Mail was set to manage the connection automatically and tried its standard list of ports. "(null)" is how macOS prints an empty value, which is why it points to a missing server name. Apple doesn't document these messages; the meanings above come from Mail's own wording and how the setting works.

Use Connection Doctor to see which server fails

Connection Doctor is still in Mail on macOS 27, even though Apple stopped describing it in its guides after macOS Ventura. It checks every account's incoming and outgoing servers.

In Mail, choose Window > Connection Doctor.
Wait for the check to finish. Each account shows a status for its incoming and outgoing server. A red dot marks the one that failed, with a short reason in the Details column.
Click Show Detail to see the conversation between Mail and the server. Lines near the end usually show the real reason, such as a rejected password.
Click Check Again after each change you make. To capture more for your provider's support team, select Log Connection Activity and click Show Logs.

If only the outgoing server fails, it's a sending problem. If only the incoming server fails, new mail won't arrive. If both fail for every account, look at your network first.

How to fix Mail not connecting to the server

1. Check your connection, VPN and network filters

Apple's first suggestion when the internet works but Mail can't reach the server is to look for a VPN or other software that monitors network connections. Turn it off, then click Check Again in Connection Doctor. Office, school and public Wi-Fi can block mail ports too, so try another network such as your phone's hotspot.

2. Rule out an outage

Check Apple System Status for iCloud Mail, or your provider's own status page. Then sign in to webmail. If webmail also fails, wait or contact the provider; there's nothing to fix in Mail.

3. Check the account's server settings

Choose Mail > Settings, click Accounts, select the account and click Server Settings.
Under Incoming Mail Server, check the Host Name isn't blank, and that User Name and Password are right.
Under Outgoing Mail Server (SMTP), make sure the Account pop-up names a server, not None. Choose Edit SMTP Server List from that pop-up to add or correct one.
Turn on Automatically manage connection settings, or turn it off and enter the port and security your provider lists (table below).
Click Save, then Check Again in Connection Doctor.

Server type	Usual port	Security
Incoming, IMAP	993	SSL/TLS
Incoming, POP	995	SSL/TLS
Outgoing, SMTP	587	STARTTLS (Mail's Use TLS/SSL)
Outgoing, SMTP (alternative)	465	SSL/TLS

Examples from providers' own pages: iCloud uses imap.mail.me.com on 993 and smtp.mail.me.com on 587. Outlook.com uses outlook.office365.com on 993 and smtp-mail.outlook.com on 587 with STARTTLS. Older guides that tell you to open ports 143 or 110 describe unencrypted connections, which most providers no longer accept.

4. Update your password or sign in again

A changed password is a common cause, and Mail may report it as a connection failure. Quit Mail, open Apple menu > System Settings > Internet Accounts, click the account and type the current password. Gmail and Outlook.com accounts need the provider's own sign-in, so remove them and add them back with the Google or Microsoft Exchange option. Details are in our guide to "Unable to verify account name or password".

5. Take the account offline and online again

Choose Mailbox > Online Status and take the account offline, then online. You can also turn off Enable this account in Mail > Settings > Accounts > Account Information, wait a few seconds and turn it back on. Both force a fresh connection.

6. Remove the account and add it back

This clears damaged settings, including the blank server behind the "(null)" error. In Mail, choose Mail > Accounts to open Internet Accounts, remove the account, then add it again and pick your provider from the list rather than "Other" where you can. Mail on IMAP, iCloud, Gmail and Exchange servers downloads again. Back up POP mailboxes first, since POP mail lives only on your Mac.

7. Update macOS

Check System Settings > General > Software Update. Mail is part of macOS, and connection bugs are usually fixed in point releases.

If Mail keeps letting you down

Disclosure: we make Canary Mail. If connection problems keep coming back across several accounts, a different app is worth a try. Canary Mail is an email app for Mac, iPhone, iPad, Windows and Android that works with Gmail, Outlook, iCloud, Yahoo, Exchange and other IMAP accounts. The free plan covers unlimited accounts on 2 devices with AI inbox sorting; the Growth plan ($36 a year) adds AI writing and summaries, read receipts and send later. More than 2 million people use it, and Apple has featured it on the App Store and the Mac App Store.

Be clear about what switching can't fix, though: if your provider is down, your password is wrong or your mailbox is full, every email app will hit the same wall.

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Frequently asked questions

Why does my email keep saying it cannot connect to the server?

Usually a network problem (VPN, firewall app or a network that blocks mail), a provider outage, wrong server settings or a changed password. Window > Connection Doctor shows which server fails and why.

What does "Connections to host (null) on the default ports failed" mean?

Mail has no server name to connect to. Open Mail > Settings > Accounts > Server Settings, fill in the Host Name or choose an outgoing server instead of None. If the fields look right, remove the account and add it back.

Where is Connection Doctor in Mail?

Choose Window > Connection Doctor. It's still there in macOS 27, Tahoe 26, Sequoia 15 and Sonoma 14, although Apple's current guides no longer describe it.

What ports does Apple Mail use?

Usually 993 for IMAP and 995 for POP (both SSL/TLS), and 587 (STARTTLS) or 465 (SSL/TLS) for sending. With Automatically manage connection settings turned on, Mail picks them for you.

Is there a current problem with Apple Mail?

Check Apple's System Status page for iCloud Mail and your provider's status page for other accounts. If webmail works, the problem is on your Mac.

How do I get Apple Mail working again?

Turn off any VPN, check the provider's status, fix the server settings and password, then take the account offline and online. If it still fails, remove the account and add it back.