Maildoso alternatives: checks to run before you switch

If you are shopping for a Maildoso alternative because your placement dropped, change one thing at a time and measure it. Mailbox vendors in this category — providers that sell bulk outreach mailboxes with the DNS pre-configured — differ in two ways that predict most of your deliverability: whose IP addresses your mail leaves on, and who administers the mail tenant. Features past that are mostly convenience.

Shared pools are the thing to ask about first

Cheap bulk mailboxes almost always send from shared IP space. That is not disqualifying — most legitimate mail in the world leaves a shared IP — but it changes who decides your fate. On a shared pool your placement moves with the complaint rates of customers you cannot see and cannot influence. One agency blasting a scraped list from the same range can cost you a week.

What to ask, and what a good answer sounds like:

Be sceptical of any comparison — including this one — that states a vendor's current pricing or feature set as fact. This category changes fast and providers disappear. Verify in writing with the provider before you sign.

Private SMTP against Google or Microsoft mailboxes

Alternatives in this space fall into two camps, and the choice is a real trade-off rather than a ranking.

Provider-run private SMTP. The vendor operates its own mail servers and IP space. You get higher per-mailbox limits, lower cost, and no third-party tenant rules. You also start from zero reputation on infrastructure that inbox providers have less reason to trust, and you are exposed to the neighbours in that IP range.

Resold Google Workspace or Microsoft 365 mailboxes. Your mail leaves infrastructure the big inbox providers already deal with at enormous scale, which helps. In exchange you accept per-mailbox sending caps, the provider's acceptable-use rules, and a tenant someone else administers — including the possibility of an account action you did not cause.

If you are sending into predominantly Microsoft 365 recipients, note that Microsoft-to-Microsoft and Google-to-Microsoft do not behave identically, and the only way to know which works for your list is to measure placement on both.

The seven-day test

Never switch an entire operation on a vendor's claim. Run this instead.

1. Keep your current mailboxes sending exactly as they are. You need a control.
2. Provision two or three mailboxes with the candidate provider, on domains you registered yourself.
3. Send one message to a mailbox you control and read the raw headers. Confirm spf=pass, dkim=pass with your own domain in the DKIM d= tag, and dmarc=pass. A DKIM signature on the vendor's domain instead of yours means your authentication is not aligned to you.
4. Resolve the sending IP's PTR record and compare it to the HELO/EHLO name in the headers. Mismatched or generic rDNS is a routine filtering trigger and a sign of a sloppy provider.
5. Check that IP and the vendor's ranges against the major blocklists. Do this before you send anything real; an already-listed IP is an inherited problem.
6. Warm the new mailboxes for at least two weeks, with gradually increasing volume and genuine two-way engagement.
7. Then measure inbox placement per provider — Gmail, Outlook, Yahoo, Microsoft 365 — on the new mailboxes and the old ones in the same week. That side-by-side is the only comparison that means anything.

What usually was not the vendor's fault

Before you pay a migration cost, rule out the causes that travel with you:

• List quality. A rising bounce rate is almost never infrastructure. Verify addresses and remove role accounts and catch-alls you cannot confirm.
• Volume ramp. New domains that go from zero to hundreds of sends a day get filtered on any provider.
• No DMARC. If you have no _dmarc record at all, publish one at p=none with a reporting address and read the reports before blaming anyone.
• Complaints. Google asks bulk senders to stay under a 0.3% reported spam rate. Nothing a vendor does will save a sequence that crosses it.
• Copy and targeting. Mail that nobody wants gets reported on every IP in the world.

What not to do

Do not buy mailboxes described as pre-warmed. Reputation is built by a sending identity engaging with real recipients over time. A mailbox that traded messages inside a vendor's pool before you owned it has no useful history, and one that has already sent cold mail for someone else has the wrong kind.

Do not run your outreach on your main company domain while testing providers. Use separate outreach domains so an experiment cannot damage the domain your invoices and support mail leave from.

Do not let the vendor hold the registrar account. Portability is the whole point of having an alternative.

Do not change provider, copy, list source and volume in the same week. You will learn nothing, and you will do it again in two months.

Where MailPilot fits

MailPilot is the measurement and warm-up layer that makes this comparison possible. It connects over OAuth to Gmail and Outlook, or over SMTP/IMAP to SendGrid, Amazon SES, Mailgun, Postmark and custom SMTP, so the same warm-up runs on whichever provider you are trialling. It checks SPF, DKIM and DMARC per sending domain, measures real per-provider inbox placement through a seed-inbox network, and tracks each mailbox's reputation daily — which turns "this feels better" into a number you can act on.