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A custom mailbox lets Prosyo send campaign emails through your own mail server (SMTP) and read replies back into your Inbox (IMAP). It works with almost any email provider.
Who can connect one#
| Plan | SMTP/IMAP mailbox |
|---|---|
| 7-day trial | 1 included |
| Starter (paid) | Not included. Starter is LinkedIn-only. |
| Multichannel | 1 included, and you can buy more |
| Agency / Team | 1 included, and you can buy more |
Need more sending mailboxes? Extra SMTP/IMAP seats are available on Multichannel and Agency / Team. See add-ons.
What you need#
- The SMTP host and port of your provider
- The IMAP host and port of your provider
- The mailbox username, usually the full email address
- The mailbox password, or an app password if your account uses two-step verification
Connect#
- Go to Settings → Accounts.
- In the Custom SMTP / IMAP card, click Add SMTP/IMAP.
- Fill in the form:
| Field | What to enter | Example |
|---|---|---|
| SMTP host | Outgoing mail server | smtp.yourdomain.com |
| Port | 587 (STARTTLS) or 465 (SSL) | 587 |
| Use SSL/TLS (port 465) | Tick only when you use port 465 | off |
| Username | Mailbox login | you@yourdomain.com |
| Password | Mailbox password or app password | •••••••• |
| IMAP host | Incoming mail server | imap.yourdomain.com |
| Port (IMAP) | Almost always 993 | 993 |
| IMAP username | Leave blank to use the SMTP username | |
| IMAP password | Leave blank to use the SMTP password | |
| From email | The address prospects see | you@yourdomain.com |
| From name (optional) | The name prospects see | Priya Sharma |
- Click Verify & connect. Prosyo tests both SMTP and IMAP before saving.
- The mailbox appears as Healthy. Your credentials are stored encrypted.
Settings for common providers#
| Provider | SMTP host | SMTP port | IMAP host | IMAP port | Password |
|---|---|---|---|---|---|
| Google Workspace / Gmail | smtp.gmail.com | 587 | imap.gmail.com | 993 | App password (turn on 2-Step Verification first) |
| Microsoft 365 / Outlook | smtp.office365.com | 587 | outlook.office365.com | 993 | Requires SMTP AUTH turned on for the mailbox. See below. |
| Zoho Mail | smtp.zoho.com (smtp.zoho.in / smtp.zoho.eu by region) | 587 or 465 | imap.zoho.com (same region) | 993 | App-specific password if 2FA is on. Turn on IMAP access in Zoho settings. |
| GoDaddy (Microsoft 365) | smtp.office365.com | 587 | outlook.office365.com | 993 | Same as Microsoft 365 |
| Hostinger | smtp.hostinger.com | 465 (SSL) | imap.hostinger.com | 993 | Mailbox password |
| Namecheap Private Email | mail.privateemail.com | 465 (SSL) | mail.privateemail.com | 993 | Mailbox password |
| Yahoo Mail | smtp.mail.yahoo.com | 465 (SSL) | imap.mail.yahoo.com | 993 | App password |
| cPanel hosting | mail.yourdomain.com | 465 (SSL) | mail.yourdomain.com | 993 | Mailbox password |
Provider settings change from time to time. If a value doesn't work, check your provider's help page for "SMTP settings".
Google Workspace / Gmail app password#
- Turn on 2-Step Verification in your Google Account.
- Open https://myaccount.google.com/apppasswords.
- Create an app password named Prosyo and copy the 16-character code.
- Paste it in both the SMTP and IMAP password fields (or only in SMTP, and leave IMAP blank).
If App passwords doesn't appear, your Google Workspace admin has turned it off. Ask them to allow it, or use the one-click Gmail / Google Workspace connection instead.
Microsoft 365 / Outlook#
Microsoft turns off basic SMTP sign-in on many tenants. If Prosyo shows an authentication error, a Microsoft 365 admin must turn on Authenticated SMTP for your mailbox:
- Open the Microsoft 365 admin center → Users → Active users.
- Select your user → Mail tab → Manage email apps.
- Tick Authenticated SMTP and IMAP, then save.
- Wait up to an hour, then connect again in Prosyo.
If your organization blocks this, use the one-click Outlook / Microsoft 365 connection instead.
Before you send: protect your domain#
For good deliverability, make sure your sending domain has:
- SPF, which lists the servers allowed to send for your domain
- DKIM, which signs your messages
- DMARC, which tells receivers what to do with unsigned mail
Your email provider's admin panel shows the exact records to add at your DNS host.
Many teams send outreach from a secondary domain (for example getacme.com instead of acme.com) so their main domain's reputation stays safe. Warm up any new mailbox: start near 25 emails per day and increase slowly.
Custom SMTP/IMAP or Gmail/Outlook?#
| Custom SMTP/IMAP | Gmail / Outlook one-click | |
|---|---|---|
| Works with | Any provider | Google and Microsoft accounts |
| Setup | Host, port and password | Sign in with Google or Microsoft |
| Replies in Inbox | Yes, via IMAP | Yes |
| Plans | Trial, Multichannel, Agency / Team | Multichannel, Agency / Team, or an extra seat |
Common errors#
| Message or symptom | Fix |
|---|---|
| Authentication failed | Check the username and password. With 2FA, use an app password. On Microsoft 365, turn on Authenticated SMTP. |
| Connection timed out | Check the host and port. Try 465 with Use SSL/TLS ticked, or 587 with it unticked. |
| SMTP works, IMAP fails | Turn on IMAP in your mail provider's settings, and check the IMAP host and port 993. |
| Emails send but no replies in Inbox | IMAP is failing. Open Settings → Accounts, click Test connection, then Sync. |
| "SMTP/IMAP isn't included in your plan" | You're on paid Starter. Upgrade to Multichannel or Agency / Team. |
Transactional emails from Prosyo itself, such as sign-in links and receipts, never use your mailbox.
