I've done a blacklist check for your host and they are clean.
SMTP CHECK:
SMTP Reverse Banner Check OK - 92.48.93.179 resolves to webhost.uk.net
SMTP Reverse DNS Mismatch Warning - Reverse DNS does not match SMTP Banner
SMTP TLS OK - Supports TLS.
SMTP Connection Time 0 seconds - Good on Connection time
SMTP Open Relay OK - Not an open relay.
SMTP Transaction Time 1.014 seconds - Good on Transaction Time
Session Transcript:
EHLO please-read-policy.mxtoolbox.com
250-daffodils.webhostpulse.com Hello mxtb-pws3.mxtoolbox.com [64.20.227.133]
250-SIZE 52428800
250-8BITMIME
250-PIPELINING
250-AUTH PLAIN LOGIN
250-STARTTLS
250 HELP [109 ms]
MAIL FROM: <
[email protected]>
250 OK [109 ms]
RCPT TO: <
[email protected]>
550-Please turn on SMTP Authentication in your mail client, or login to the
550-IMAP/POP3 server before sending your message. mxtb-pws3.mxtoolbox.com
550-(please-read-policy.mxtoolbox.com) [64.20.227.133]:59740 is not permitted
550 to relay through this server without authentication. [312 ms]
QUIT
221 daffodils.webhostpulse.com closing connection [125 ms]
Reverse lookup is working fine
Your issue is with that I've highlighted, there SMTP record is wrong. So when email is sent out and authenticated against another mail server, it's reading the record and saying hang-on that's not where this email came from and is automatically marked as spam.
To fully prove that is what is happening, whats your domain.