TL;DR

Most connection issues: Go to Settings → Sending Settings, click trash icon to unlink email, then reconnect with correct SMTP/IMAP settings (verify host, port, SSL enabled, correct credentials). For 'Invalid Grant' errors: Unlink email in Settings → Sending Settings, then reactivate. For timeout errors: Verify no IP restrictions, check host/port with SSL enabled, confirm no provider outages.

Symptoms

Email account shows Disconnected or Error status in Settings
Error message: "Invalid Grant" when connecting Gmail/Google Workspace
Connection timeout when trying to connect email
Campaigns paused with message about email connection issues
Cannot send test emails from connected account

Environment

Applies to all email providers connected to lemlist via SMTP/IMAP or OAuth (Gmail/Google Workspace).

Note: Some SMTP providers are not supported: SendGrid, Mailgun, Sendinblue, Mailjet, O2switch, Amazon SES, Postmark, Cloudmark, HostGator. Use different provider if using these.

Step-by-Step Fix

1. Verify SMTP/IMAP configuration

Check these settings match your email provider:

SMTP settings:

Host and port correct for your provider
SSL/TLS enabled
Username (email address) correct
Password correct

IMAP settings:

Host and port correct for your provider
SSL enabled
Same credentials as SMTP

Common ports:

SMTP: 465 (SSL) or 587 (TLS)
IMAP: 993 (SSL)

✅ Verify: Settings match provider documentation exactly

2. Reconnect email account

Go to Settings → Sending Settings

Click trash icon next to problematic email

⚠️ Note: This pauses campaigns temporarily

Click Add email and reconnect with updated settings

Test connection after reconnecting

✅ Verify: Email shows Connected status

3. Check email permissions

Verify your email provider allows third-party app access:

Gmail/Google Workspace:

Check Google Account security settings
Ensure "Less secure app access" enabled (if applicable)
Verify OAuth permissions granted

Other providers:

Check provider security settings
Enable IMAP access if disabled
Generate app-specific password if using 2FA

✅ Verify: Provider allows external app connections

4. Rule out connectivity blocks

Check:

Firewall not blocking SMTP/IMAP ports
No IP restrictions from email provider
Browser cache cleared
Using latest browser version

✅ Verify: No network or firewall blocks

Fix Specific Errors

Invalid Grant Error (Gmail/Google Workspace)

Cause: Expired OAuth token or revoked permissions

Fix:

Go to Settings → Sending Settings
Click trash icon to deactivate email
Click Add email to reactivate
Re-authorize when prompted

✅ Verify: Can send test email without errors

Connection Timeout

Cause: IP restrictions, incorrect settings, or provider outage

Fix:

Verify host and port correct with SSL enabled
Check no IP restrictions blocking lemlist servers
Contact provider to confirm no outages
Try different network if on restricted corporate network

✅ Verify: Connection completes without timeout

Provider-Specific Settings

Zoho Mail

Enable IMAP: Settings → Email Accounts → Configure IMAP
Use these settings:
- IMAP: imappro.zoho.com (Port 993)
- SMTP: smtp.zoho.com (Port 465)
Generate app-specific password if using 2FA

Lark

Manually type settings (don't copy-paste)
Enable SSL encryption
Verify all required fields filled
Confirm credentials valid in Lark settings

Confirm It's Fixed

✓ Email account shows Connected status in Settings

✓ Test email sends successfully

✓ Paused campaigns resume automatically

✓ No error messages in Sending Settings

Why It Happens

Connection issues occur when SMTP/IMAP settings are incorrect, OAuth tokens expire, email providers block third-party access, or network firewalls block connections. Providers may also have temporary outages or security restrictions.

Prevent this: Use correct provider settings, keep OAuth permissions current, enable IMAP access, generate app-specific passwords for 2FA accounts.