Email Problem

verjin

Recently I migrated emails to my server (cPanel with MailChannels) (around 12 June) and since then customer is having problem with specific email addresses (specifically in sending).

If he sends (using Outlook/Thunderbird/MailSpring and other clients) any email to specific email address from his office/home (different computer/mobiles devices) it bounce back. He also run multiple tests via mail-tester/sparkpost/dkimvalidator (and you name it) all fails and shows DKIM/SPF/DMARC has issue.
(When he tries to send via webmail (Roundcube/Horde) no issue and it works just fine)

When I do the same (as he did) from my end, everything passes and works like a charm (no bounceback, DKIM/SPF all are validated without single error).

I am unable to understand what causing the issue, would it be email client (thunderbird,outlook) somehow modifying email headers (If yes then he already ran with different devices and clients) ? Or is it something related to their ISP or local firewall settings? I can provide test email header if you need to look into.

Thanks everyone, any help or suggestion would be great.

berkay

Could it be that he forgot to change the configuration to point to the current server? Did he try to remove the account from any and every client completely and added it back from scratch?

Mr_Tom

As above, check the client isn't still sending from the old config. Their email client sounds like it has incorrect SMTP details. You could get them to email you from webmail and their client, and comapre headers?

Not_Oles

@verjin said: If he sends (using Outlook/Thunderbird/MailSpring and other clients) any email to specific email address from his office/home (different computer/mobiles devices) it bounce back.

Maybe I am missing something. You seem to be saying that the bounce occurs only when one user is sending remotely through your MTA via SMTP to a single destination email address. Do I understand correctly? From where does the email bounce? Is it the destination MTA that is rejecting the email? Can you post your MTA's logs for one of the bounced emails? Best wishes from Mexico!

verjin

@berkay said:
Could it be that he forgot to change the configuration to point to the current server? Did he try to remove the account from any and every client completely and added it back from scratch?

Everything is setup from scratch.

@Mr_Tom said:
As above, check the client isn't still sending from the old config. Their email client sounds like it has incorrect SMTP details. You could get them to email you from webmail and their client, and compare headers?

On email header comparison I find X-MC-Relay is set to Junk in bounce email and X-MC-Relay is set to neutral in delivered email header.

@Not_Oles said:

@verjin said: If he sends (using Outlook/Thunderbird/MailSpring and other clients) any email to specific email address from his office/home (different computer/mobiles devices) it bounce back.

Maybe I am missing something. You seem to be saying that the bounce occurs only when one user is sending remotely through your MTA via SMTP to a single destination email address. Do I understand correctly? From where does the email bounce? Is it the destination MTA that is rejecting the email? Can you post your MTA's logs for one of the bounced emails? Best wishes from Mexico!

I will share more details with you @Not_Oles

Not_Oles

@verjin said: I will share more details with you @Not_Oles

Excellent!