Here are practical ways (and concrete commands) you can use to find IMAP server for an email address or domain. I’ll include how to try each approach and what to look for.
1) Check the provider’s documentation / support site
Most email providers publish their IMAP/SMTP settings. If the address is @gmail.com, @yahoo.com, @outlook.com, etc., a quick support page search (or the provider’s help center) gives the exact host and port.
2) Use automatic configuration endpoints (autoconfig / autodiscover)
Many mail providers expose autoconfig that email clients use:
Thunderbird-style autoconfig URL:
https://autoconfig.example.com/mail/config-v1.1.xml
https://example.com/.well-known/autoconfig/mail/config-v1.1.xml
Microsoft/Exchange Autodiscover:
https://autodiscover.example.com/autodiscover/autodiscover.xml
If those URLs return XML, the file often contains IMAP host, port, and security settings.
3) Inspect DNS records
a) MX records — MX tells you which host receives mail for the domain. Sometimes the IMAP server is at the same host or follows a similar naming pattern.
Use:dig MX example.com +shortnslookup -query=MX example.com
If MX is mx1.example.net, try imap.example.net or mail.example.net.
b) SRV records — some services publish service records:
_imap._tcp.example.com
Check with:dig SRV _imap._tcp.example.com +shortnslookup -type=SRV _imap._tcp.example.com
If there’s an SRV record it gives the host and port for IMAP.
4) Try common hostname patterns
Many hosts use predictable names. Try these (replace example.com):imap.example.com
mail.example.com
mailhost.example.com
imap-mail.example.com
Often the secure IMAP (implicit TLS) is on port 993; non-TLS or STARTTLS uses port 143.
5) Use an email client’s auto-setup
Create a new account in Thunderbird, Outlook, Apple Mail, or your phone’s mail app and enter the email and password — the client’s auto-configuration will usually discover IMAP settings automatically and show them.
6) Probe servers with network tools (no credentials required)
These tell you whether a guessed host is listening on IMAP ports.
Check DNS A/AAAA for hostname
dig +short imap.example.com
Test TCP connectivity
telnet imap.example.com 143 (may show greeting or nothing if closed)
telnet imap.example.com 993
or nc -vz imap.example.com 993
Check TLS handshake (useful for port 993):
openssl s_client -connect imap.example.com:993 -crlf
If you see an X.509 certificate and connection opens, that host is serving IMAP over SSL.
STARTTLS on 143:
openssl s_client -starttls imap -connect imap.example.com:143
If the server supports STARTTLS, you’ll get a valid TLS handshake.
Service discovery / scanning (use carefully & legally):
nmap -sV -p 143,993 imap.example.com
This can reveal that an IMAP server is running and its software/version. Only scan hosts you’re authorized to test.
7) Look up the email provider by domain (common providers)
If the domain is a public provider, common IMAP servers include:
Gmail: imap.gmail.com (port 993)
Yahoo: imap.mail.yahoo.com (port 993)
iCloud: imap.mail.me.com (port 993)
Outlook/Office365: outlook.office365.com (or imap-mail.outlook.com, port 993)
(These are examples — always verify in the provider docs.)
8) Online lookup / third-party tools
There are online tools and lookup pages that attempt auto-configuration or show common server settings for a domain. Use them if you trust the site — don’t enter credentials into unknown tools.
9) Contact admin / support
If the email is for a company/domain you don’t control, ask your IT support or domain admin — they’ll give the exact IMAP host, ports, and any special security requirements (VPN, special certificates, etc.).
10) What not to do
Don’t try to brute-force ports/credentials. That’s illegal/abusive.
Don’t paste real passwords into random online tools or share them with untrusted sources.
Quick example sequence you can run locallydig MX example.com +short → see mail exchangersdig +short imap.example.com → check hostname resolvesopenssl s_client -connect imap.example.com:993 → test IMAPSopenssl s_client -starttls imap -connect imap.example.com:143 → test STARTTLS
If those fail, try https://autoconfig.example.com/mail/config-v1.1.xml in a browser.