Custom domain email mobile setup on iPhone and Android takes about 10 minutes per device once you know the IMAP and SMTP settings. The Apple Mail app, the Gmail app, and the Android default Mail app each have a slightly different setup flow but use the same underlying credentials. The settings change rarely; learn them once and the same configuration works across every device the operator owns.
Most "custom domain email mobile" walkthroughs cover one app and one OS. Operators usually need to configure mail on at least two clients — Apple Mail on iPhone plus Gmail app or Outlook on Android, or vice versa. The three flows below cover the common combinations with the same underlying settings.
This guide walks the iPhone, Gmail app, and Android Mail flows with one shared settings table. For the broader frame see custom domain email.
What You Need Before Starting
Before starting, gather three pieces of information: the mailbox address (you@yourcompany.com), the mailbox password or app password, and the IMAP and SMTP server hostnames the mailbox host uses. The mailbox host's dashboard usually exposes all three in a single "client setup" or "device configuration" page — have them ready before opening the mobile app.
If the mailbox host requires app passwords (separate from the account password) for IMAP and SMTP, generate one before starting the device setup. Some hosts also require enabling IMAP access in the dashboard before clients can connect. The setup goes faster if these prerequisites are done before opening the mobile app.
Shared IMAP and SMTP Settings
IMAP and SMTP settings are identical across every mobile client for the same mailbox host. The table below shows the standard configuration for a TrekMail-hosted custom domain email mobile setup. The values work across Apple Mail, the Gmail app, and Android Mail without modification.
| Setting | Value | Notes |
|---|---|---|
| IMAP server | imap.trekmail.net | For receiving mail |
| IMAP port | 993 | SSL/TLS required |
| IMAP security | SSL/TLS | Don't use STARTTLS on port 143 |
| SMTP server | smtp.trekmail.net | For sending mail |
| SMTP port | 465 (SSL) or 587 (STARTTLS) | Both work; 465 is preferred |
| Username | full email address | you@yourcompany.com |
| Password | mailbox or app password | App password if 2FA is on |
The settings table is reusable across every device. Save a copy somewhere accessible — password manager, shared team note, or printed card — so future custom domain email mobile setup sessions don't require looking up the settings again. Most operators configure mobile clients three or four times across iPhone upgrades, Android rotations, and new team member onboarding. The settings stay the same throughout; only the device changes.
iPhone Apple Mail Walkthrough
The iPhone custom domain email mobile setup in Apple Mail takes about 5 minutes. Open Settings, scroll to Mail, tap Accounts → Add Account → Other. Tap Add Mail Account. Enter Name, Email (you@yourcompany.com), Password, and Description. Tap Next to proceed to the server-settings screen.
Apple Mail tries to auto-discover the server settings. Most custom domains don't have auto-discover records published, so the auto-detection fails and you get a manual entry screen. Enter the IMAP and SMTP settings from the shared table above. Apple Mail verifies the credentials and saves the account. The new mailbox appears in the Mail app immediately and syncs over the next few minutes.
Gmail App Walkthrough (Android & iPhone)
The Gmail app custom domain email mobile setup uses the "Other" account type. Open the Gmail app, tap the profile icon, tap Add another account → Other. Enter the email address and tap Next. Pick "Personal (IMAP)" rather than Exchange. Enter the password and tap Next.
The Gmail app walks through IMAP and SMTP server settings on subsequent screens. Use the values from the shared settings table. The app confirms the configuration and adds the mailbox alongside any existing Gmail accounts. Switching between mailboxes happens through the profile-icon dropdown. The custom domain mailbox uses the same Gmail interface as gmail.com mailboxes — the same search, labels, and filters work across all accounts. That unified experience is the main reason many operators prefer the Gmail app over native Apple Mail or Android Mail for custom domain email mobile setup.
Android Default Mail Walkthrough
The Android custom domain email mobile setup on the default Mail app (Samsung Email, Mi Mail, Pixel — varies by manufacturer) uses the "Other email account" option. Open the Mail app, tap the menu icon, tap Settings → Add Account → Other. Enter the email address and password.
The app tries auto-discovery first. When auto-discovery fails (as it usually does for custom domains without auto-discover records), choose Manual setup, then IMAP. Enter the IMAP and SMTP settings from the shared table. The app validates the credentials and saves the account. Some manufacturers' default Mail apps have slightly different UI but the underlying flow is the same. See email with own domain for the broader setup walkthrough.
App Password vs Account Password
Some mailbox hosts require an app password rather than the regular account password. App passwords are device-specific credentials that bypass two-factor authentication for clients that don't support 2FA prompts. Generate one from the mailbox host's dashboard, enter it on the device during the custom domain email mobile setup, and revoke it when the device leaves use.
TrekMail supports app passwords through the dashboard's account-security section. Each app password is one-time-displayed at generation; copy it before closing the dialog. Use a different app password per device so revoking one doesn't disrupt the others. A device lost or wiped gets its app password revoked; every other device in the custom domain email mobile setup continues working.
Two-Factor Authentication on Mobile
Two-factor authentication works through app passwords on most mobile clients. The mailbox host's web UI requires 2FA for login; mobile clients use the app password (already authenticated through 2FA when generated). The result is 2FA-protected account access without 2FA prompts on every sync.
Hardware-key 2FA is preferred for the admin account; software-based 2FA (TOTP) works for regular accounts. Set up 2FA before starting the custom domain email mobile setup so the app-password flow is available when needed. The 30 minutes at 2FA configuration prevents the most common account-takeover pattern affecting custom-domain mailboxes running without 2FA protection.
Common Troubleshooting
Three issues show up consistently in the custom domain email mobile setup. First, account fails to verify — usually a TLS certificate mismatch from typing the wrong server hostname. Re-check IMAP/SMTP hostnames against the settings table above. Second, mail receives but sending fails — usually an SMTP port issue (try 465 if 587 fails, or vice versa).
Third, the account verifies but mail doesn't sync — usually IMAP isn't enabled in the mailbox host's dashboard. Enable IMAP access from the host's web UI, then wait 5 minutes before retrying on the device. Each issue has a 2-minute fix once you know to look for it. Documenting these three fixes in onboarding materials saves support time. See forward email to Outlook for the desktop-client adjacent topic.
Next Steps
The custom domain email mobile setup takes about 10 minutes per device using the shared IMAP and SMTP settings from the table above. Apple Mail, Gmail app, and Android Mail all work with the same credentials without modification. App passwords combined with 2FA on the web UI provides security without 2FA prompts on every mobile sync.
Test TrekMail Nano free at trekmail.net/pricing — no card required, no trial expiry. The Nano tier covers 10 domains × 10 mailboxes; Starter at $4/month ($42/year) expands to 50 × 100 when send volume grows past the free tier's cap.
The custom domain email mobile setup is one of the few configurations operators repeat across the device lifecycle. iPhone upgrades, Android rotations, new team members joining — each event triggers another setup round. Saving the IMAP/SMTP settings table somewhere accessible (password manager, shared team note) compresses future setups to about 5 minutes per device instead of starting from scratch each time.
The other observation is that the custom domain email mobile setup on Android typically defaults to the Gmail app, while iPhone operators split between Apple Mail and the Gmail app. Both are credible choices. The Gmail app's main advantage is consistent UI across personal Gmail accounts and custom-domain mailboxes in one interface. Apple Mail's main advantage is deeper integration with iOS notifications, the Siri suggestions system, and the Mail extension ecosystem. Pick whichever fits the device workflow — deliverability and feature differences between the two clients are negligible.
For team rollouts of the custom domain email mobile setup, add the IMAP/SMTP settings table to onboarding documentation. New hires configure mobile devices in 5 minutes without operator help. The 15 minutes spent writing the doc pays off at every subsequent new-hire device setup. See email with own domain for the broader setup walkthrough.
