Issues with Outlook Account Blocking in HubSpot Sequences Due to Email Bounce and SPF/DKIM Configuration | RevGenius

Md R.
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Hey Ashwin - common pattern with HubSpot Sequences through M365 when DKIM isn't enabled. Good news: it's fixable without touching the DNS records that affect inbound mail. Quick mental model that might help: SPF, DKIM, and DMARC are the three records receiving filters check on OUTBOUND email. They're separate from MX records, which control INBOUND. Adding or fixing SPF / DKIM / DMARC won't stop you receiving mail. The change that broke inbound previously was almost certainly MX-related, which is a different category of fix. Three things to do, in order: 1. Enable DKIM in M365 (Exchange admin center → mail flow → DKIM, enable for your domain). M365 will generate two CNAME records (selector1._domainkey and selector2._domainkey) you publish at your domain host. New records - they don't conflict with anything existing. 2. Audit your SPF: confirm both Microsoft AND HubSpot are included in your domain's SPF TXT record. If you've got a lot of includes already, watch the 10-lookup limit (SPF fails silently if you exceed it). 3. Publish a DMARC record at p=none with a reporting address. Lets you watch for 7-14 days who's actually authenticating and who isn't before you raise enforcement. The Outlook spam-block usually clears within a few days of auth being clean, because the receiving filters stop classifying you as an unauthenticated sender. The 5-bounce trigger is M365 being conservative when it can't verify you. Happy to run a quick public-data scan on your sending domain offline if useful - DM me and I'll send back a one-pager with the specific findings.
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Ayush S.
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In addition what Riaz already told you, make sure you are not using a new domain. You should actually be using a warmed up sub-domain so such incidents do not affect your primary domain and warm up the sub-domain for some time as email service provviders like google, microsoft mark them as spam/junk or land in promotions/updates faster than warmed up old ones.
Jordan
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Along with the comments above, a few other things I’d consider: If you have new reps, don’t have them jump straight into external outbound at full volume. Give the mailbox a little time to warm up first. Start with internal messages that are likely to get replies. Something simple like, “I’m new and would love to set up time to connect,” plus 1-2 relevant questions works well. After about a week, start very slowly with external emails. I’d also flag IT so they can watch for any early signs from Outlook or Google that the user or domain is getting flagged. For the first day, I’d keep it around 5-10 external emails, spread throughout the day. Ideally, start with messages that are more likely to get responses. In the past, webinar recording follow-ups or “Do you have any questions?” emails have worked well. From there, add volume slowly. For the rest of week one, I’d only increase by a few external emails per day and continue spacing them out. Don’t send them all at once. During week two, you can gradually increase volume, but I’d still keep it measured and watch engagement closely. The more personalized and reply-driven those early emails are, the better. By weeks three and four, most mailboxes can usually handle a higher outbound volume. Even then, continue spreading sends throughout the day across all reps. Consistent sending behavior is just as important as the total volume. Also watch your link-to-text ratio. For first-touch outreach, I’d keep links minimal and avoid loading the email with multiple CTAs or tracked links.
Jared R.
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this sequence of responses is absolutely epic and super comprehensive!
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