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Email settings
SMTP, IMAP, and POP3 configuration for 218 providers worldwide. Ports, hostnames, TLS modes, authentication, and the small details that break clients when you get them wrong.
Email settings are the tactical layer where things break. Your provider says port 587, your client is configured for 465. Your SMTP works but IMAP fails. Your Outlook wants OAuth2 but your relay script uses password auth. Small mistakes cost hours of debugging.
This hub covers both directions of that problem. On one side, 218 provider-specific configuration guides: Gmail, Outlook, iCloud, GMX, all the way down to regional ISPs still serving millions of legacy addresses. On the other side, the protocol-level cornerstones: SMTP setup, IMAP configuration, POP3, email forwarding, and SSL/TLS for both client submission and MTA-to-MTA transport.
Every provider page is verified against live servers. Protocol guides ground themselves in the RFCs that actually define what should happen. Where providers deviate from spec (they all do somewhere), we say so.
★Provider directory
Find your provider
218 email providers with verified POP3, IMAP, and SMTP settings. Browse the catalog by name, country, or ISP.
Protocol setup
SMTP, IMAP, POP3 walkthroughs with port tables, authentication modes, and TLS variants.
Read guides →Popular providers
Gmail, Outlook, Yahoo, iCloud, GMX: server names, ports, and modern client configuration.
Read guides →SSL and TLS security
STARTTLS vs Implicit TLS, MTA-STS, DANE, TLS-RPT, certificate requirements.
Read guides →Email forwarding
SMTP-level relay, SRS rewriting, and why forwarding breaks DMARC without care.
Read guides →SMTP setup
Ports 25 / 465 / 587, LOGIN vs OAuth2, app passwords, testing with openssl and swaks.
Read guides →IMAP configuration
Port 993 default, folder mapping, simultaneous connection limits, testing checklist.
Read guides →For modern setups: SMTP submission uses port 587 with STARTTLS or port 465 with Implicit TLS. IMAP uses port 993 with Implicit TLS. POP3 uses port 995 with Implicit TLS. Port 25 is reserved for MTA-to-MTA relay and is not for client submission. Ports 143 and 110 (plain IMAP and POP3) are legacy and should only be used with STARTTLS enforced.
STARTTLS starts the connection in plaintext, then upgrades to TLS via a command. Implicit TLS negotiates TLS from the first byte. Both are secure when properly configured. Match the port to the mode: 587 expects STARTTLS, 465 expects Implicit TLS. A client configured for the wrong mode will fail to connect.
Prefer OAuth2 when the provider supports it and your client can implement it (modern desktop clients, mobile clients, most SDKs). App passwords work as a fallback for legacy clients, scripts, and self-hosted MTAs where OAuth2 setup is disproportionate. Gmail and Microsoft 365 both accept both; Yahoo and iCloud lean toward app passwords for third-party clients.
The most common cause is port and TLS mode mismatch on the SMTP side. IMAP defaults are stable (993 Implicit TLS almost universally). SMTP requires matching the correct port with the correct TLS mode and authentication method. A secondary cause: ISPs and corporate firewalls sometimes block outbound port 587 or 465, which does not affect IMAP retrieval.
IMAP keeps mail on the server and syncs state across devices: mark a message read on your phone, it shows read on your laptop. POP3 downloads mail to the local device and (by default) deletes it from the server. IMAP is the modern default for multi-device use; POP3 makes sense only for single-device, offline-first workflows with tight storage constraints.
Publish a DNS TXT record at _mta-sts.yourdomain.com and host the policy file at https://mta-sts.yourdomain.com/.well-known/mta-sts.txt. Test with Hardenize or the official MTA-STS validators. Start in "testing" mode with TLS-RPT enabled, verify reports for two to four weeks, then switch to "enforce".