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Outgoing SMTP blocked—residential IP reputation on VPS?

VPS Hosting by techmei 22 replies 2.1K views
techmei

Member OP

#1

Since 2 week my mail from VPS will bounce, the IP reputation is bad they say. I have two server with Contabo, one in EU one in APAC, both same /24 block maybe? My `dig` show same upstream. The SMTP port 25 not blocked by them, but gmail and outlook will reject. I check mxtoolbox, all green except one "poor sender reputation". How to fix this, will I need dedicated IP? My use case is just cron report and personal notification, volume very low. I am not spammer XD

dig +short myip.opendns.com @resolver1.opendns.com

The IP show 203.0.113.45, and reverse DNS is generic. I ask Contabo support, they say "IP reputation is customer responsibility". But I just open account 3 month ago... this IP maybe used before? How do you check previous owner reputation damage. Thank you for any help.

garykwh

Member

Inference on a Budget

#2

Ngl this is why I just use LLM APIs for everything now, no SMTP headache lol. But srsly—IP reputation is basically VRAM for email, once it's burned good luck training a new one

Your provider's whole /24 might be cooked from some previous tenant doing crypto spam or whatever. Check Spamhaus PBL and SBL listings for the /24, not just your IP: https://www.spamhaus.org

CUDA cores are my love language
srelet

Member

#3

This is a classic case of inherited technical debt with zero transparency from the provider. At my last gig we had a postmortem exactly like this—turned out our block had been resold three times without any reputation tracking.

techmei said:
Contabo support, they say "IP reputation is customer responsibility"

That's... not transparency. That's deflection. You should demand they disclose:

  • When that IP was last assigned
  • Whether they monitor block-level reputation
  • Their error budget for IP provisioning (spoiler: probably none)

I checked Spamhaus for 203.0.113.0/24. It's listed. The entire /24, since March. Previous customer was running bulletproof hosting apparently. Contabo knows. They just hope you don't look.

Sven3

Member

Stockholm

#4

Oh, obviously Contabo has excellent transparency here, or whether they do not? How do you say... their support is clearly the gold standard of accountability /s

srelet said:
They just hope you don't look

I appreciate that you think this requires detection, but I must correct your sarcasm detection—this is not subtle. It is a flashlight in a dark room. A very dark room. Filled with spiders.

My advice: migrate. Or stay and enjoy your permanent residence in gmail's junk folder. The /24 is dead, your IP is dead, your cron reports are dead. Long live the cron reports. /s

HO

Member

#5

Which Contabo region is the EU one, Nuremberg or Düsseldorf

techmei

Member OP

#6

Nuremberg for EU one. I check Spamhaus now thanks to srelet, yes PBL listed. Not my fault but I am the one suffering. Contabo say they can change IP for 2.99 EUR but no guarantee new one is clean. This feel like lottery. — https://www.spamhaus.org

HO

Member

#7

St. Louis and New York are the US ones, Singapore or Tokyo for APAC. Nuremberg is the old DC, Düsseldorf newer. Not that it matters if the whole ASN is dirty.

Ray

Member

#8

I had same with a residential ISP block in 2021. Forward your cron to something like Mailgun free tier, 5000/month. Save yourself the IP warming headache entirely.

techmei

Member OP

8 #9

Mailgun need domain verify and they ask business use case. Personal notification maybe too small for them? I look at SendGrid also but same feeling.

MeritBudi

Member

#10

Same here with Contabo Mumbai. Three month account, same problem. I just route through AWS SES now, 62k free if from EC2 but my VPS not qualify. Still cheap at $0.10 per 1000. Not worth fighting IP reputation.

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