Response issue - No autoresponse when original sender was from an external address.

Dear Ben,

> When we receive an email from an external source, there is no autoresponse being sent out to them.
> If the email is sent internally, the response does work.
>
> As an example occurrence of this:
> In the error log, we get this at the time a response should be sent -
> 21/2/2018 11:02:26.618 - [SMTP Server(SMTP Server) - 513] - Aborting autoresponse (service) because return path is NULL
>
> In the mail log, we get this -
> : 21/2/2018 11:02:26 - Sent Mail to VPOP3 for Local: (Test Email)
> : 21/2/2018 11:02:26 - Routed Mail to (Test Email)
>
> We collect our emails from Gridhost.
> Looking at the above logs, it looks as though the address vpop3 uses to send reply's or identify the sender are being stripped by our host.
>
> Is there a specific email header field that vpop3 requires in order for the response to work?
> The only field in the headers currently containing the sender address is the envelope-from field.
> The return-path field shows as: (Which to me would represent a null value in most cases)
>
> Thank you in advanced.
>

I'm sorry, but it appears that you do not have an active maintenance or support agreement with us. Because of this, your message has been moved into a low priority queue where we will try to answer it over the next several 5-10 working days. Note that for out-of-maintenance support we cannot go into detail or spend a lot of time on the problem.

If you need a more urgent response, or the problem is complex, you should take out a maintenance or priority support agreement.

An annual maintenance agreement costs 25% of the full licence fee and includes email technical support and software version upgrades. All new licences include 1 year of maintenance.(Maintenance runs from the previous expiry of your maintenance, so if it expired over a year ago you may be better taking out priority support).

An annual priority support agreement costs 50% of the full licence fee and includes priority email technical support, and telephone and remote support during UK office hours. This can be taken out even if maintenance has lapsed.

You can buy maintenance or support agreements online at https://www.pscs.co.uk/helpdesk/purchase.php

Alternatively you can use our free online self-service resources:
- our knowledgebase at https://wiki.pscs.co.uk
- our support portal, including forum at https://helpdesk.pscs.co.uk/

Solutions to many questions and problems can be found by searching the above resources. For instance, if you have received an error message from VPOP3, try searching for the error message text or subject of the error message email. About 80% of the support queries we receive have already been answered in our knowledgebase.

> When we receive an email from an external source, there is no autoresponse being sent out to them.
> If the email is sent internally, the response does work.
>
> As an example occurrence of this:
> In the error log, we get this at the time a response should be sent -
> 21/2/2018 11:02:26.618 - [SMTP Server(SMTP Server) - 513] - Aborting autoresponse (service) because return path is NULL

The Return-Path header should show where the message came from. I guess SendGrid are changing that for some reason (you'd have to ask them what they're doing).

The Internet standard for automatic responses say that automated responses should go back to the Return Path email address, except when it is blank, in which case an automated response should not be sent at all. (RFC 3834 section 4)

So, because SendGrid seem to be doing something unusual and is blanking out the return-path header, you'll have to stop VPOP3 from following the standards. Go to Settings -> Autoresponder Settings, and turn off "Make autoresponders conform to RFC 3834". This will make VPOP3 respond to the From address of the incoming message instead of the return-path address.

Note that this can cause mailing loops if the sender email address also has some form of automated response, so be extra sure that you configured the autoresponder in VPOP3 not to respond to the same sender address within several hours, to try to prevent loops.