How to connect Gmail via SMTP/IMAP so that reply detection works

If you want to send proposals from your Gmail address and use reply detection, you need to connect your mailbox via SMTP/IMAP. Google no longer allows logging into such connections with your regular account password — instead, you need to use what's called an app password. Below you'll find the complete requirements and a step-by-step guide.

Why doesn't the regular password work?

For security reasons, Google has disabled logging in with a regular password for external applications connecting via SMTP/IMAP (for personal accounts since 2022, and for business Google Workspace accounts since 2025). That's why, when you try to connect with a regular password, errors like these appear:

• SMTP Error: 534 5.7.9 InvalidSecondFactor - the account has two-step verification enabled, but a regular password was used. An app password is required.

• SMTP Error: 535 5.7.8 BadCredentials - Google rejected the login credentials. Most often because a regular password was used instead of an app password, or because of an incorrect login/password. If the account doesn't have 2FA, you must enable it first, because without it an app password cannot be generated.

The solution in both cases is to generate an app password and enter it in Sellizer instead of your standard password.

What you need (requirements)

Before you start, make sure that:
1. You have a Gmail or Google Workspace account (a business address on a domain managed by Google).
2. Two-step verification (2FA) is enabled on the account — without it, Google won't allow you to generate an app password.
3. You know the login credentials for this account (they'll be needed to enable 2FA and generate the password).

Important (business / Google Workspace accounts): if you use a business address, your organization's administrator must have enabled the ability to use app passwords as well as IMAP access. If the option to generate an app password doesn't appear despite 2FA being enabled, contact your domain administrator.

Step 1. Enable two-step verification (2FA)

Note: If you already have 2FA enabled, go straight to Step 2.

1. Log in to your Google account and go to Manage your Google Account (click your avatar in the top-right corner → Manage your Google Account, or go to https://myaccount.google.com).
2. Go to the Security section (in the left-hand menu).
3. Select 2-Step Verification.
4. Click Turn on and follow the instructions.
5. When finished, a green On status should appear next to "2-Step Verification".

Step 2. Generate an app password

1. Go directly to the app passwords page: https://myaccount.google.com/apppasswords (log in again if needed).
2. in the app name field, enter any name, e.g. Sellizer.
3. Click Create.
4. Google will display a 16-character app password (a string of letters).
5. Copy this password right away - once you close the window, it will no longer be visible. If you lose it, simply generate a new one.

You can enter the app password with or without spaces - both forms work.

Step 3. Connect the mailbox in Sellizer

1. In Sellizer, go to the mailbox configuration: Settings → Mail. Choose the option "I have another email" (connection via SMTP/IMAP).
2. Fill in the fields:

• Login: your full email address (e.g. firstname.lastname@yourdomain.com)

• Password: paste the app password from Step 2 (not your regular account password!)

• SMTP host: smtp.gmail.com, port 465 (SSL) or 587 (STARTTLS/TLS)

• IMAP host: imap.gmail.com, port 993 (SSL)

3. Confirm. If the details are correct, the mailbox will be connected and you'll be able to send proposals from your address.

Most common problems

No "App passwords" option despite 2FA being enabled.
This most often affects business accounts (Google Workspace) - the administrator must allow app passwords and IMAP access. Contact your domain administrator.