Most cold email that lands in spam was decided before anyone wrote a word of copy. The list had addresses that no longer exist, the domain was a week old, and one mailbox was asked to send four hundred messages on a Tuesday. Cold email deliverability is mostly a question of who you send to and what you send from, and only after that a question of what you say.
We split that work with a partner. QuickMail is an Oneprofile integration partner, and the split is simple: Oneprofile decides who gets an email and makes sure their address is real, and QuickMail runs the mailboxes the email leaves from. This post is the playbook for that handoff, plus a few opinions about deliverability that have nothing to do with either product.
What cold email deliverability depends on
Deliverability is the share of your messages that reach an inbox. Not the spam folder, and not a bounce. Gmail, Outlook and the other inbox services decide that per message, and they lean on three groups of evidence:
The addresses. A message to an address that does not exist bounces, and a high bounce rate tells them you send to lists you have not checked.
The sender. Your domain's age, its SPF, DKIM and DMARC records, how long each mailbox has been warming, and how much it sends in a day.
The reaction. Replies help. Spam complaints hurt a lot, and people quietly ignoring you hurts a little over time.
Google publishes its version of the rules in its email sender guidelines. Every sender has to authenticate with SPF or DKIM, and bulk senders are asked to keep the spam rate reported in Postmaster Tools under 0.3%. Cold outreach rarely hits the bulk threshold from a single mailbox, but the direction is clear. Inbox services reward senders whose mail people want.
The three groups are not equal. The first one is the only one you fully control before you hit send, which is why it is where we start.
Cold email deliverability starts with the list
A bounce is the cheapest deliverability mistake to prevent and one of the most expensive to make. The address either exists or it does not, and you can check before the message ever leaves.
Say you pull 600 people from a search and 40 of the addresses are stale. If all 600 go out on day one, the domain posts a bounce rate near 7%. Most of what we have read from people who run deliverability for a living puts the safe ceiling somewhere around 2%, and a new domain gets less benefit of the doubt than an old one.
So in Oneprofile the order is fixed: find, verify, then send. You search for people by job title and company, or bring the list you already have. Oneprofile fills in work emails from 75+ data sources and runs each one through Verify email. Every address comes back valid, invalid or catch-all.
What to do with each result:
Valid goes into the campaign.
Invalid stays out. There is no version of this where sending to it helps.
Catch-all means the domain accepts everything, so nobody can tell from the outside whether the person exists. Send these as their own small batch, ideally from one mailbox, and watch the bounces.
The list is also where relevance comes from. A message that could have gone to anyone gets ignored, and ignored mail slowly teaches the inbox service that you are not wanted. Oneprofile researches each prospect and can write an opening line from that research, so the first sentence is about them. We will come back to why that matters for deliverability and not only for replies.
Where QuickMail does the work: mailboxes, warmup and inbox rotation
Once the list is clean, the rest of deliverability is infrastructure, and this is the part QuickMail is built for. They have been running cold outreach since 2014, and their product covers the jobs that usually sprawl across several tools: buying and configuring sending domains, warming new mailboxes, monitoring blacklists, and rotating sends across inboxes.
Inbox rotation is the piece people underrate. A campaign that sends from one mailbox puts all its reputation on that mailbox. Spread the same campaign across several warmed mailboxes and each one sends a modest number of messages a day. If one starts landing in spam, it can come out of rotation while the others keep going.
QuickMail also watches the signals for you. Deliverability insights and blacklist monitoring flag a mailbox that is getting into trouble before the replies dry up, which is usually the first moment anyone notices.
None of this rescues a bad list. Rotation spreads bounces across mailboxes, so it slows the damage, but every one of those mailboxes still takes the hit. That is the reason we like the split: each side fixes a different cause.
Moving verified leads from Oneprofile into QuickMail
Today the handoff between the two is a CSV, and it takes a few minutes per campaign:
Filter to the segment. Keep leads whose email came back valid and who fit the campaign. Catch-all addresses go into a separate export.
Name the fields you will use. Give each field the campaign needs a short header with no spaces, such as
first_name,companyandopening_line.Export the file. Click the table's name, then Export to file, then Export to CSV. The export follows your filter and field order, and it costs no credits.
Import into a QuickMail campaign. Upload the file and map each header to a QuickMail field or a custom field, so
opening_linebecomes a variable in your copy.Send the catch-all batch last. Give it its own campaign and a single mailbox, and stop it if bounces climb.
Our guide to importing enriched leads into a sequencer walks through the field mapping in more detail, including how to mark the campaign in your CRM so reps can see who is mid-sequence.
If you would rather keep everything in one place, Oneprofile runs email and LinkedIn sequences itself. The split with QuickMail makes the most sense when your sending already lives there, or when you run outreach for several clients and want their mailboxes kept apart.
Measuring deliverability without fooling yourself
Here is an opinion that has nothing to do with either product: open rates stopped being a deliverability metric a while ago. Apple Mail Privacy Protection preloads images, so plenty of messages register an open whether or not a person read them. A dashboard that shows a 70% open rate on a cold campaign tells you very little.
The numbers worth watching are blunter:
Bounce rate per campaign. If it climbs, the list is the problem, and you can fix it upstream.
Reply rate per mailbox. A mailbox whose replies fall off while its siblings hold steady is probably landing in spam.
Spam complaints, where you can see them. Google Postmaster Tools shows the rate for your domain once you send enough volume.
Placement tests, where you send to seed inboxes and see which folder each lands in, are useful but a bit of a snapshot. We would not run a campaign on them alone.
Back to the opening line, as promised. Relevance looks like a copywriting concern, but inbox services read engagement, and people reply to messages that are clearly about them. A first sentence written from the person's own research is a deliverability tool as much as a reply tool.
Anyway, the short version: verify every address before it leaves, send from warmed mailboxes that share the load, and write to fewer people with a better reason. Oneprofile handles the first and the last. QuickMail handles the middle.