Sending to a Gmail account issue

[#1]

I have Outlook 365 on Win 11.  I can send emails to various address except to a Gmail address.  The reason given is as follows;

Reason: A message that you sent to the following recipient could not be delivered due to a permanent error. ** The remote server ?? responded with: ** xxxxxxx@gmail.com ??:?? This message was created automatically by mail delivery software on the server .

I have had this issue for awhile.   I do not have an issue receiving gmail.  This is very annoying and hope it can be resolved.  How can I resolve this issue?  Thanks.

[#2]

@Surfer are you sending from an <accountname>.plus.com email address or do you have your own domain address ?

[#3]

I am sending using a xxxx@pobox.com and I use relay.plus.net for outgoing mail so going via plus net.  I only having this issue when sending to a Gmail address.

[#4]

I am sending using a xxxx@pobox.com

@Surfer Ah! I suspected as much. You need to ensure that your domain has an SPF record that specifies the plusnet mail server as a permitted sender. Google have insisted that any mail sent to gmail addresses must have either SPF and/or DKIM authentication.

Where is your domain hosted ?

[#5]

Not sure if I understand, but the "pobox.com" is based in the USA where Gmail originated anyway.  I have no idea what SPF and/or DKIM authentication is or how to resolve it.  In my ignorance I would have thought that email sent would be going out via Plus net as using the SMTP for plus net and not the SMTP for Pobox.com.  I have been using the "Pobox" domain for probably 15-20 years, but the Gmail issue only cropped up recently.  As you can gather I am not that computer savvy when it comes to these sort of things so many thanks for all the help.

[#6]

Not sure if I understand, but the "pobox.com" is based in the USA where Gmail originated anyway.

It doesnt matter where the domain is based , what matters is that the mail server via which you send must be 'authorised' to send mail for that domain. See here https://proprivacy.com/email/guides/what-is-spf for an explanation of SPF.

Lets be clear, SPF is not a mandatory standard BUT google decided unilaterally last year that mail to gmail addresses MUST comply with it!.

I had assumed that pobox.com was your personal domain but it appears it is not. It is a general mail service.

It does have an SPF record which defines its own mail servers, you need to change your outgoing SMTP server to the pobox ones. Deatils should be here https://www.pobox.help/hc/en-us/sections/360012235293-Setting-up-your-email-application

[#7]

An SPF record lists what SMTP servers are allowed to be used to legitimately send email from.  For pobox.com, the records show that it can use:

• 64.147.108.0/24
• 173.228.157.0/24
•  spf.messagingengine.com

The first 2 are ranges of IP Addresses, and the last one will be another SPF record with other IP addresses/ranges of IP addresses.

None of those will be Plusnet's SMTP servers.

A receiving mailserver will check that record and will reject/increase the chance of marking it as spam if it hasn't come from one of those servers.

The SPF record actually says to "soft fail" any messages that fail, which should mean they are marked as spam, but Gmail (the free version, not the paid version) is rejecting anything that fails now.

[#8]

Thanks I will query it with Pobox when they start work at about 1pm and post an update if any.  👍

[#9]

Just to add on checking the Pobox Help section I came across this;

Is DKIM or SPF available for messages sent via SMTP?

All messages sent via the SMTP server are DKIM-signed with Pobox's DKIM key.  SPF is available for MyPobox personal domains. It is not available for Pobox's domains (@pobox.com, @rightbox.com, etc.), because rules are domain-based, and not all Pobox customers send mail via the SMTP servers.

I am not sure if I understand the above?

[#10]

That is either out of date, or plain wrong.  If you check the pobox.com domain you can see the SPF record for it, which is what I posted above.  Here it is: https://mxtoolbox.com/SuperTool.aspx?action=spf%3apobox.com&run=toolpage

[#11]

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@Surfer wrote:

I am sending using a xxxx@pobox.com and I use relay.plus.net for outgoing mail so going via plus net.  I only having this issue when sending to a Gmail address.

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And that is core to the issue - Plusnet's servers are not deemed legitimate senders for this third party domain ... why not simply use their SMTP server for out going emails?