I'm using Microsoft 365 Exchange Online to send emails from my domain, techoffice.ca, but I'm running into issues with Gmail rejecting all outgoing messages. I'm receiving a '550 5.7.350' error, indicating that Gmail suspects my emails are spam because of a low domain reputation. I've made sure that SPF, DKIM, and DMARC are all properly set up and passing. The Google Postmaster Tools aren't showing any data for my mail because it's being rejected at the SMTP level. It appears that my sending IP is an IPv6 from Microsoft's shared pool, which may be contributing to a bad reputation. I can't force my emails to go out over IPv4 or control the IP rotation from my end, and unfortunately, Microsoft's support hasn't been much help. I'm hoping to connect with others who might have faced this issue, especially using Microsoft 365. Any advice on whether Microsoft can route emails over better IPs, suggestions for escalating this problem, or whether I should temporarily switch to a smart host for Gmail?
1 Answer
Are you sending out marketing emails? If so, you might want to avoid that for now. Microsoft might be using its "low confidence" IP pool for your messages, which is where they send emails that aren’t outright spam but could be perceived as annoying. Consider using a third-party service like Mailgun for those kinds of emails and make sure to set up a subdomain for sending, complete with separate SPF, DKIM, and DMARC settings to protect your main domain's reputation. Gmail is strict about spam reports, so any significant activity there can hurt your reputation.
Yes, we do send service proposals to multiple contacts, and it's been a hassle because we can't even reply to incoming Gmail messages. I’m definitely considering using a different service for marketing emails to keep things cleaner. Any additional advice would be great!