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Short answer
Download the Mailshake CSV from Outreach2day; its 11 columns are Mailshake's template. In Mailshake click Mail Accounts > Add Account > Bulk Import and upload it; the import takes 15 minutes to 2 hours and Mailshake emails the status of each account. Then set Max emails per day to 25 in the Sending Calendar; warm-up keeps running in Outreach2day.
What you get
- A CSV in Mailshake's import format with the SMTP and IMAP settings of every mailbox you pick
- Warm-up keeps running in Outreach2day after the export, included in the price
- SPF, DKIM and DMARC already set on every domain
Export the CSV and import it into Mailshake
In Outreach2day
- Select mailboxes. Open Mailboxes and select the mailboxes to export, or export all of them
- Download the file. Click Export and pick Mailshake. The CSV downloads with one row per mailbox
In Mailshake
- Open Bulk Import. In the left menu click Mail Accounts, then Add Account, then Bulk Import (docs.mailshake.com)
- Upload. Drag the file to the Upload box or click Choose File, then Import. The file must be under 5 MB (docs.mailshake.com)
- Wait for the email. Imports take 15 minutes to 2 hours; Mailshake emails a status for each account (docs.mailshake.com)
- Or add one mailbox. Mail Accounts > + Add Account > SMTP, enter the address, name, SMTP and IMAP host, port, username and password, then Next (docs.mailshake.com)
Fields in the Mailshake CSV
The file from the Mailshake export has these columns:
| Column | Value |
|---|---|
from_name | Sender first and last name |
from_email | The mailbox address |
smtp_host, smtp_port | outreachmailstream.com, 465 |
smtp_username, smtp_password | The address and the mailbox password |
imap_host, imap_port | outreachmailstream.com, 993 |
imap_username, imap_password | The address and the mailbox password |
warmup_enabled | true |
- The 11 columns are the ones in Mailshake's CSV template, in the same order; ports 465 and 993 are in the template's allowed lists
- warmup_enabled true turns on Mailshake's warm-up as well; Outreach2day warm-up already runs, so set it to false if you don't want both
- The file has no daily limit column: set it in Mailshake after the import
Connection settings
To add a single mailbox by hand, or to check what Mailshake saved, use these settings:
| Field | Value |
|---|---|
| SMTP host | outreachmailstream.com |
| SMTP port | 465 (SSL/TLS) |
| IMAP host | outreachmailstream.com |
| IMAP port | 993 (SSL/TLS) |
| Username (SMTP and IMAP) | The full email address |
| Password (SMTP and IMAP) | The mailbox password from the export (the same for SMTP and IMAP) |
Sending settings per mailbox
- Mailboxes can send cold email 14 days after warm-up starts; warm-up keeps running after that
- Up to 25 cold emails per mailbox a day, warm-up not counted
- Start low on day 14 (for example 5 a day) and reach 25 around day 21
- To send more, add mailboxes and domains; keep the per-mailbox number at 25
Where to set it in Mailshake:
- Max emails per day per address: Sending Calendar > Settings > Custom > Edit (set 25; needs a Mailshake Admin) (docs.mailshake.com)
- Mailshake's own cadence starts at 20 a day in week 1; for Outreach2day mailboxes stop at 25 (docs.mailshake.com)
- Minutes between sends: Mailshake suggests at least 5 (docs.mailshake.com)
Why 25: how many cold emails one mailbox should send a day. The day-by-day ramp: email warm-up schedule.
Warm-up
Warm-up for Outreach2day mailboxes runs in Outreach2day and is included in the price. It keeps running after you export the mailboxes, whichever tool sends from them, so the other tool's warm-up is optional.
- Mailshake's warm-up settings: Deliverability > Email Warmup > Accounts > gear icon: Max Daily Emails Per Day, Reply Rate %, Increase Gradually to Daily Send Volume (docs.mailshake.com)
Keep warm-up on while the mailbox sends: should I keep warm-up running while sending.
DNS and tracking domain
- SPF, DKIM and DMARC for every Outreach2day domain are set and checked automatically; you add nothing for sending
- A custom tracking domain is a CNAME on a subdomain of your sending domain. For a domain whose DNS Outreach2day hosts, add it in the app: Domains, open the domain, Manage DNS records, Add record (type CNAME). For a domain whose DNS stays at your registrar, add it there
- A tracking domain matters only with open or click tracking on. In the first cold email, leave out the tracking pixel and links and measure replies (see the answer on open tracking below)
- Mailshake's custom tracking domain is a CNAME on any subdomain pointing to tracking.mailshake.com, set in Settings > Team Settings > Tracking Domains; one tracking domain per team, http links only (docs.mailshake.com)
More on tracking: do open tracking and links hurt cold email deliverability.
Troubleshooting
| Error or symptom | Fix |
|---|---|
| The CSV file format is incorrect. Some required fields or headers are missing. | A column is missing or out of order: download the Mailshake file from Outreach2day again and upload it unchanged (docs.mailshake.com) |
| Import status: Added, connection error | The login or the server settings are wrong; check them against the settings on this page (docs.mailshake.com) |
| Internal Error / Inbox Checking Settings Incorrect | Usually authentication: recheck the IMAP settings (993, SSL) and the password (docs.mailshake.com) |
| Import status: Duplicate, updated | Not an error: the account was already in Mailshake and was updated from the file (docs.mailshake.com) |
| Authentication failed / invalid credentials | Use the full email address as the username and the password from a fresh export. A disabled mailbox is exported with an empty password, so it can't connect |
| Connection timed out or SSL/TLS handshake error | Use SMTP port 465 with SSL/TLS and IMAP port 993 with SSL/TLS, both on outreachmailstream.com. Check that the tool did not switch the security setting to STARTTLS or none |
| Mailbox connects but can't send yet | Check the mailbox in Outreach2day: new mailboxes are being set up for up to 24 hours, and cold email starts 14 days after warm-up starts |
| Mailbox disconnected after it worked | Reconnect it in the tool with the same settings. With a one-click connection (Instantly, Smartlead) and auto-reconnect on, Outreach2day reconnects it for you |
If bounces climb after the mailboxes connect, look at the list: why a cold email bounce rate gets too high.
FAQ
Does the Mailshake CSV from Outreach2day match Mailshake's template?
Yes. It has the same 11 columns in the same order as the template linked from Mailshake's bulk import article (checked on 2026-10-09).
Can I add mailboxes to Mailshake through its API?
Mailshake's public API lists senders but has no endpoint to create a mail account, so use Bulk Import or add accounts one by one.
Do I need Mailshake's warm-up for Outreach2day mailboxes?
No. Warm-up for Outreach2day mailboxes runs in Outreach2day and keeps running after you add them to Mailshake.
Sources
Mailshake documentation, read on 2026-10-09. Menus and field names change; if a step differs, Mailshake's own page is the reference.
- Mailshake: Upload and connect multiple sending addresses: docs.mailshake.com/article/410-how-do-i-upload-and-connect-multiple-sending-email-addresses
- Mailshake: Send emails with SMTP: docs.mailshake.com/article/189-how-do-i-send-emails-with-smtp
- Mailshake: How many emails can I send per day: docs.mailshake.com/article/57-how-many-emails-can-i-send-per-day
- Mailshake: Tweak sending schedules: docs.mailshake.com/article/140-how-can-i-tweak-sending-schedules
- Mailshake: Change warm-up settings: docs.mailshake.com/article/294-how-do-i-change-my-warm-up-settings
- Mailshake: Customize link tracking: docs.mailshake.com/article/138-how-do-i-customize-link-tracking
- Mailshake: Internal error when connecting SMTP: docs.mailshake.com/article/250-why-am-i-receiving-an-internal-error-or-inbox-checking-settings-incorrect-error-message-when-connecting-smtp
