Been doing outbound at scale for a couple years now, and I keep seeing the same questions pop up. So here's the stuff I actually learned, so I can stop copy-pasting the same DMs.

Lesson 1: Google Workspace and Office 365 are your friends

Moved to GWS and Office 365 sending infrastructure. There are a handful of providers now - PuzzleInbox, Maildoso, Mailforge, Hypertide. I still keep some Microsoft inboxes in the mix at lower send rates. Diversity protects you.

Lesson 2: Domains are cheap, your time isn't

Porkbun. Buy in bulk. Five to ten alternates per brand (gettheBrand, trybrand, brand-hq, etc). Max three inboxes per domain. Twenty to thirty sends per inbox per day. If a domain gets burnt - and they will - don't try to save it. Write it off. People spend hours trying to "rehab" a flagged domain when a new one costs eight quid. DMARC, SPF, DKIM set up properly. Cloudflare for DNS. Half the "my deliverability sucks" posts are people who never aligned SPF correctly. Fifteen minutes of work per domain.

Lesson 3: Your sending habits matter more than your tool

Used most of them: Instantly, Smartlead, Salesforge, Quickmail, Lemlist. They all work, they all have quirks. Smartlead is my daily driver because the master inbox and API are solid at scale. Instantly has the cleaner UI but gets sluggish past 100+ inboxes. Quickmail is underrated for follow-up-heavy sequences. Pick one and learn it deeply instead of jumping around. What actually moves the needle isn't the tool though - it's:

Plain text only. No HTML, no images, no fancy signature.
No links in the first email. Ask a question that needs a reply. Replies are the single strongest deliverability signal.
Spintax everything (subject, body, CTA) so no two emails are technically identical.
TURN OFF OPEN TRACKING. The pixel hurts you and Apple/Gmail lie about opens anyway. Measure reply rate only.
Twenty to thirty sends per inbox max. More inboxes, not more sends per inbox.

Lesson 4: Data is where money gets burned

People waste so much money here. ZoomInfo is rarely worth it. Apollo gets you eighty percent of the way for a fraction of the price. Clay is the brain of everything if you're serious. Enrich through a waterfall of providers, AI-personalise the opener from a real signal (recent post, hiring, funding, whatever), then push to your sending tool. Yes, it's expensive. Pays for itself in a week if you know what you're doing. A couple underrated tools nobody talks about enough: LeadMagic for waterfall, Prospeo for catchall validation, Trigify for buying signals from LinkedIn activity.

Lesson 5: Verify or die

Don't send to unverified lists - ever. One bad blast and your domains are toast. Million Verifier for standard, Reoon for catchalls. That's it. NeverBounce is overpriced.

Lesson 6: Warm up forever

Run warmup for at least two to three weeks before sending real outreach from a new inbox. Then keep it running at ten to fifteen a day forever. People turn it off to save resources and wonder why their sender rep slowly dies over six months.

Lesson 7: The offer matters more than the infrastructure

Learned this the hard way multiple times. You can have the cleanest setup, perfect copy, best data - if the offer sucks, none of it matters. Spent a year optimising the wrong thing. If reply rates are low, first question shouldn't be "is my deliverability bad?" It should be "is what I'm offering actually compelling to this audience?"

Lesson 8: Timing

Mon/Tue/Wed for B2B. Thurs/Fri performance falls off a cliff. Nobody wants to start a new conversation going into the weekend.

Bonus - a tool nobody mentions

RB2B for deanonymising website visitors. Someone visits your pricing page after your message hits their inbox? That's your warmest lead of the week. Call them Monday. I've closed real money this way.