Google Workspace vs Microsoft 365 vs SMTP for Cold Email

Cold email mailboxes come in three kinds: Google Workspace accounts, Microsoft 365 (Exchange Online) accounts and SMTP/IMAP mailboxes from an email infrastructure vendor. Every major sequencer connects all three. Google and Microsoft give you the mail platform recipients know best, at $4 to $7 a user a month on Microsoft's US annual plans, and both say in their own terms or docs that their mailboxes are not for bulk or unsolicited mail. SMTP/IMAP mailboxes cost $2 to $5 a month, are sold for outbound and carry no tenant-wide limits, but come from a smaller provider whose reputation you share. The right choice depends on your recipients, your volume and the sequencer you keep.

Facts below come from Google's, Microsoft's and each sequencer's own pages, checked October 9, 2026. We sell SMTP/IMAP mailboxes, so we also say where Google or Microsoft fits better.

The Three Mailbox Types at a Glance

Google Workspace: Limits and Rules

Google's Gmail sending limits for Workspace:

• 2,000 messages a day per user (1,500 by mail merge, 500 on a trial account), over a rolling 24 hours

• 10,000 total recipients a day, 3,000 external recipients and 3,000 unique recipients (2,000 external)

• Trial limits stay low until the domain has paid at least $100 in total, which can take up to 75 days

Google's sender guidelines apply to all mail sent to Gmail users: keep the Postmaster Tools spam rate below 0.10% and never reach 0.30%. Senders of more than 5,000 messages a day to personal Gmail accounts must also meet the bulk-sender rules, including one-click unsubscribe for marketing mail.

Policy: Google's Acceptable Use Policy forbids using the service for unsolicited mass email, and its program policies describe spam as unsolicited mail to significant numbers of addresses with no pre-existing relationship. A cold program on Workspace runs inside those terms, which is why teams keep it to a few emails a day per mailbox. More on the numbers: Google Workspace sending limits.

Microsoft 365: Limits and Rules

Microsoft's Exchange Online limits:

• 10,000 recipients a day per mailbox and 30 messages a minute

• Up to 1,000 recipients per message

• A tenant-wide external recipient limit (TERRL) of 500 × (licenses ^ 0.7) + 9,500 a day; at 1,000 licenses that is 72,446 (Microsoft announcement)

• Trial tenants get a lower external cap: 5,000 a day on the Learn page, 500 in the TERRL announcement (the two Microsoft sources disagree)

• Default onmicrosoft.com domains can send to 100 external recipients a day per organization

The per-mailbox external limit of 2,000 recipients a day that Microsoft had planned for 2026 was cancelled indefinitely on January 6, 2026. Microsoft's limits page says customers who need legitimate bulk commercial email should use a third-party provider. On the receiving side, Outlook.com rejects mail from domains sending over 5,000 a day without SPF, DKIM and DMARC with error 550 5.7.515 since May 5, 2025 (Microsoft). More: Microsoft 365 sending limits.

Microsoft lists Exchange Online Plan 1 at $4 a user a month and Microsoft 365 Business Basic at $7, both paid yearly (Exchange Online plans, Microsoft 365 business plans).

SMTP/IMAP Mailboxes From a Vendor

An infrastructure vendor creates mailboxes on your domains on its own mail servers and gives you SMTP and IMAP logins, or connects them to your sequencer for you. Prices checked October 9, 2026:

The trade-off: SMTP mailboxes are cheaper and built for outbound, and you avoid Google's and Microsoft's tenant rules. Some recipients' filters treat mail from Google or Microsoft servers with more trust, and a shared sending pool means other senders affect you. Domain reputation stays yours in all three cases, which is why authentication, list quality and a low daily volume per mailbox matter more than the mailbox type.

Mailbox Types by Sequencer

Instantly

• Connects Google (OAuth for Workspace, app password for personal Gmail), Microsoft (OAuth, one account at a time) and any IMAP/SMTP provider; IMAP is required (connect accounts)

• Recommends 30 campaign emails a day per account; AirMail accounts are capped at 50 (campaign options)

• Warm-up is unlimited and included in every Outreach plan; warm at least 2 weeks, 3 for AirMail

• Sells done-for-you Google accounts at $5 a month, pre-warmed Google at $10 and AirMail SMTP at $4, with domains at $15 a year. Instantly keeps the domains and the accounts work only inside Instantly (details)

• Plans from $47 a month with unlimited email accounts (Instantly pricing)

Smartlead

• Connects Google (OAuth or SMTP/IMAP), Outlook by OAuth (with authenticated SMTP and IMAP enabled) and any SMTP/IMAP provider

• Recommends 15 to 25 emails a day for Google mailboxes bought through it (SmartSenders FAQ)

• Warm-up is included in every plan

• SmartSenders: Google or Outlook through Zapmail at $4.50 a mailbox plus $13 a domain a year, SMTP through Mailreef at $3.99 plus $19, pre-warmed at $9 plus $18. They can't be used outside Smartlead (SmartSenders pricing); Smartlead's own FAQ still lists older prices

• Plans from $39 a month with no per-mailbox fee; its blog of September 25, 2026 leaves the Google or Microsoft choice to what you know (Smartlead pricing)

lemlist

• Connects Google (OAuth through the Gmail API), Microsoft (OAuth) and IMAP/SMTP; SendGrid, Mailgun and SES are not supported (connect a provider)

• Recommends starting at 10 to 15 emails a day, adding 5 a week up to 25 to 30, with warm-up and campaigns together at 50 a day or less (account limits)

• lemwarm is included in all plans

• Sells Google and Outlook mailboxes from $10 a month and SMTP from $5, with a domain locked for one year and no refunds; Google buyers get Admin Console access

• Email plan $69 a month for 50,000 emails with unlimited senders (lemlist pricing)

Apollo

• Basic allows one mailbox per user; Professional connects unlimited Google Workspace and Microsoft 365 mailboxes plus up to 5 custom IMAP/SMTP per user, Organization up to 15 (Apollo mailboxes)

• Recommends 50 to 100 emails a day, starting at 50 per mailbox (sending limits); mailboxes bought from Apollo are capped at 200 a day

• Warm-up covers one mailbox per seat; each extra mailbox costs 200 credits per 30 days, with a recommended maximum of 40 warm-up emails a day (Apollo warm-up)

• Sells mailboxes for credits: Apollo SMTP 300 credits a month, Google Workspace 800, Microsoft 365 1,500, a domain 1,500 credits a year. Apollo asks for at least 6 weeks of warm-up on them. The dollar value of a credit is not published, so the cost per mailbox can't be computed

Reply.io

• Connects Google and Microsoft by OAuth and any SMTP/IMAP provider; buys Google or Microsoft mailboxes (warm-up guide)

• Hard cap of 400 emails a day per account on paid plans, 200 on trial; the default ramp starts at 10 a day (limits)

• MailToaster warm-up is included, one seat per connected mailbox

• Pre-warmed Google or Microsoft mailboxes at $15 a month plus $25 a domain a year, 3 per domain; extra connected mailboxes on the Multichannel plan cost $29 a month each (pre-warmed, pricing)

• Reply.io's pages block automated reads; these facts were read in a browser

Summary by sequencer

Our own recommendation is 25 cold emails per mailbox a day after warm-up, on top of warm-up traffic (why 25).

What 100 Mailboxes Cost by Type

Mailboxes only, monthly, US list prices where published. The sequencer plan is the same whichever type you connect.

Add domains: at 5 mailboxes per domain, 100 mailboxes need 20 domains, $260 a year at $13 a .com. The cold email capacity calculator sizes the setup from your daily volume.

When Google Workspace or Microsoft 365 Is the Right Choice

• Most of your recipients are on Google or on Microsoft, you send a few hundred emails a day, and you want the platform they trust; some teams split mailboxes between the two to match their list

• You need full mailbox features for each sender (calendar, Drive or Teams, a real inbox the rep uses daily)

• Your sequencer's in-house accounts are Google or Microsoft and you never plan to leave it

• Your security team requires a Google or Microsoft tenant for any mail sent under the company's domains

Keep the volume per mailbox low on both, set SPF, DKIM and DMARC on every sending domain, and watch the tenant limits on new Microsoft tenants.

When SMTP/IMAP Mailboxes Are the Right Choice

• You run more than a few dozen mailboxes and the per-mailbox price drives the bill

• You want one vendor to create the domains, DNS and mailboxes and keep warm-up running

• You run several sequencers or clients and want mailboxes that connect to any of them

• You want to avoid tenant-wide limits and Google's and Microsoft's terms on unsolicited mail

Or Skip the Separate Sequencer

Outreach2day is a mailbox vendor and a sequencer in one product. Keep your sequencer and use our mailboxes at $2.50 each, or run everything in Outreach2day: mailboxes on your domains, warm-up and campaigns with multi-step sequences, schedules, stop on reply, a unified inbox where you answer replies, and stats for sent, replies and bounces, for the same $2.50 a mailbox. It is email only (no LinkedIn or calls), has no lead database and offers SMTP/IMAP mailboxes only, with no Google or Microsoft option. Running 1,000 mailboxes or more? We quote a volume price below every vendor list price in our comparisons; book a call with our deliverability team.

For a deeper look at moving off Google, see Google Workspace alternatives for cold email; for SMTP itself, SMTP for cold email.

FAQ

Is Google Workspace or Microsoft 365 better for cold email?

Neither provider supports cold email in its terms: Google forbids unsolicited mass email and Microsoft says Exchange Online is not suited to bulk commercial mail. Microsoft allows more recipients per mailbox (10,000 a day against Google's 3,000 external), and is cheaper per user on US list prices ($4 for Exchange Online Plan 1). Match the provider to where most of your recipients are, and keep the volume per mailbox low on either.

Can I use SMTP mailboxes with Instantly, Smartlead, lemlist, Apollo and Reply.io?

Yes. All five connect SMTP/IMAP accounts. Instantly requires IMAP as well as SMTP; Apollo allows up to 5 custom IMAP/SMTP mailboxes per user on Professional and 15 on Organization.

How many cold emails can one mailbox send a day?

The platforms allow far more than is safe for cold email. Sequencers recommend 15 to 30 a day per mailbox (Smartlead, lemlist, Instantly), Apollo 50 to 100. We recommend 25 a day after warm-up.

Did Microsoft add a 2,000 external recipient limit per mailbox?

No. Microsoft cancelled the planned mailbox external recipient rate limit indefinitely on January 6, 2026. The 10,000 recipients a day per mailbox and the tenant-wide external limit still apply.

Do SMTP mailboxes land in spam more often than Google or Microsoft mailboxes?

Placement depends mostly on domain reputation, authentication, list quality and volume per mailbox, which you control on all three types. The mail servers matter too: some filters trust Google and Microsoft servers more, and a shared SMTP pool carries other senders' reputation. Test with a small volume to your actual recipients before scaling.

Which mailbox type does Outreach2day sell?

SMTP/IMAP mailboxes on your own domains at $2.50 a month, with warm-up and a sequencer included. We do not sell Google Workspace or Microsoft 365 seats.

Sources

Checked October 9, 2026:

• Google: Gmail sending limits in Workspace, email sender guidelines, Acceptable Use Policy, program policies, Workspace pricing

• Microsoft: Exchange Online limits, tenant outbound limits, mailbox external limit cancelled, Outlook.com high-volume sender rules, Microsoft 365 business plans and Exchange Online plans (read in a browser)

• Instantly: connect accounts, campaign options, pricing.md, AirMail

• Smartlead: pricing, SmartSenders pricing, SmartSenders FAQ, Google Workspace vs Office 365 blog

• lemlist: connect a provider, account limits, buy a domain and email, plans

• Apollo: mailboxes, sending limits, warm-up

• Reply.io (read in a browser): limits, warm-up, pre-warmed mailboxes, pricing

• Mailforge: pricing