SOLVED 550 Invalid RCPT (thank you for using SPF)

Hello team

I hope you are doing great! I am wondering if you can assist with the following. I know there are many topics on this issue - though mine seems to be unique as far as I can tell !!

I keep getting mail bouncing back to one single email address and I cannot seem to identify where/what the issue is - whether this is a setting on my server - or if it is the remote server. There are no other issues on my server.

Email has been working fine to the recipient - until yesterday and now I get a bounce back (below) from my server - regardless of what I send them. There have been no changes on my server (other than a recent upgrade to version 62 build 15).

I am hoping you might be able to tell me if this is an issue with their domain or with the receiving server - or if I should add something to my cpanel config?

I have not seen this exact message before - especially the 550 Invalid RCPT "thank you for using SPF" - which I have googled but found no matches!!

I've checked my sending server IP in blacklists and all is fine. However, I did notice that their domain does not have an SPF record. Could that be the issue - though I assumed SPF was more for "sending" rather than receiving (Sender Policy Framework). Could the absence of an SPF cause recipient issues?

Strangely - if they send me an email - I seem to be able to reply without issue. Also I tried send them an email from my personal Gmail account - that bounced too.

I have contacted their domain host and waiting for their reply - perhaps my sending server is blocked by them?

Thanks in advance.

 

Hello - problem solved - I finally discovered the mail host had inadvertently suspended the account without any notification to the customer! Needless to say, problem solved by moving them to a new host!