• Status: Solved
  • Priority: Low
  • Security: Public
  • Views: 92
  • Last Modified:

SMTP error from remote mail server after initial connection: 501 PTR hostname must resolve to IP

SMTP error from remote mail server after initial connection:
    501 PTR hostname must resolve to IP
sophy ska
sophy ska
  • 2
3 Solutions
Sam Simon NasserIT Support ProfessionalCommented:
check the solutions here

and as mentioned on spiceworks https://community.spiceworks.com/topic/1420914-501-ptr-hostname-must-resolve-to-ip
quick update, used "MXtoolbox" to look up our domain, entered our public ip - that is connected to our mailserver

an received

Type: PTR

IP :  our correct IP

Domain name : mail.domainname.com

TTL: 24hrs

dns lookup =

reported by ns1.virginmedia.net on 2/1/2016 etc etc....

so this looks ok - to my untrained eye

You need to ask your ISP to add a Reverse DNS (PTR) Record for you with your domain name.

They will know exactly what this means, and only your ISP can do that for you - its not something you can generally do yourself.

Dr. KlahnPrincipal Software EngineerCommented:
If you're on a dynamic DNS connection where your IP address can change without notice or a "static IP" connection from an ISP without proper RDNS, then the only real solution for this problem is to route outgoing mail through a third party such as SMTP2Go.  I find it easier to route mail through them anyway; they take care of a lot of issues that are tedious and annoying for a standalone MTA.

SMTP2Go will route up to 1,000 outgoing emails a month free of charge.

Solutions / answers provided.
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Featured Post

Cloud Class® Course: Python 3 Fundamentals

This course will teach participants about installing and configuring Python, syntax, importing, statements, types, strings, booleans, files, lists, tuples, comprehensions, functions, and classes.

  • 2
Tackle projects and never again get stuck behind a technical roadblock.
Join Now