1 Topic by wh.leong

  • wh.leong
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Topic: Cannot receiving email from sender where their smtp keep changing

Hi Huangbin

We encountered an issue where they cannot receive email from some external party like from Tencent. Upon checking, it seems that their smtp server / smtp server IP addresses keeps changing and a temporary workaround solution is to whitelist the sender email address.

May I check is there a way to resolve this issue permanent other than whitelisting the sender email address?
Thanks.

Regards
Wai Hong

----

Spider Email Archiver: On-Premises, lightweight email archiving software developed by iRedMail team. Supports Amazon S3 compatible storage and custom branding.

2 Reply by dave.opc

  • dave.opc
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Re: Cannot receiving email from sender where their smtp keep changing

stop changing ip addresses

3 Reply by wh.leong

  • wh.leong
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Re: Cannot receiving email from sender where their smtp keep changing

dave.opc wrote:

stop changing ip addresses


May I know what do you mean? We don't change our smtp server IP addresses. However, emails from external parties which we do not have any control may use a dynamic IP address and thus, what will be the best course of action to resolve this issue? Thanks.

4 Reply by dave.opc

  • dave.opc
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Re: Cannot receiving email from sender where their smtp keep changing

the thing is - that's not your issue. They have to stop changing ip addresses. You rather let them know about their issue, or disable spam filters, or enable whitelist.
if we are talking about tencent.com specifically then:

ERROR: No reverse DNS (PTR) entries. The problem MX records are:
59.167.51.121.in-addr.arpa -> no reverse (PTR) detected
100.248.205.203.in-addr.arpa -> no reverse (PTR) detected
You should contact your ISP and ask him to add a PTR record for your ips

5 Reply by wh.leong

  • wh.leong
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Re: Cannot receiving email from sender where their smtp keep changing

dave.opc wrote:

the thing is - that's not your issue. They have to stop changing ip addresses. You rather let them know about their issue, or disable spam filters, or enable whitelist.
if we are talking about tencent.com specifically then:

ERROR: No reverse DNS (PTR) entries. The problem MX records are:
59.167.51.121.in-addr.arpa -> no reverse (PTR) detected
100.248.205.203.in-addr.arpa -> no reverse (PTR) detected
You should contact your ISP and ask him to add a PTR record for your ips

Hi Dave.

Thanks for the update.
However, this is not specifically targeted to Tencent domain. There are other domains like qq.com (which is also Tencent), Ant Group, Alibaba, etc. which will also use dynamic IP for their domain instead. Even some of our government agency also use dynamic IP address as it is more secure. Question is how do we have a permanent solution to fix this issue rather than just whitelisting them which is very inefficient. I believe that there are other users who is also facing similar issue and how do you advise them to permanently fix the issue.
Thanks.

6 Reply by wh.leong

  • wh.leong
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Re: Cannot receiving email from sender where their smtp keep changing

Hi Dave and Huangbin.

May I check is there any way to permanently resolve this issue? Thanks.

7 Reply by ZhangHuangbin

  • ZhangHuangbin
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Re: Cannot receiving email from sender where their smtp keep changing

Try to disable greylisting service for these big companies.

Tencent / QQ / Alibaba / ... have their own email servers, i GUESS when email is rejected temporarily (4xx smtp code), they change IP addresses to retry immediately, so that they can quickly send out the email instead of staying in queue for hours or even days.

Yahoo had same issue before, but i forgot how it goes now.