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What kind of problem have you encountered?

Does your domain provided in MAIL FROM address use SPF policy?

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Most common delivery errors

554 Message refused by the scanner

  • Ordinary emails: Send us your original rejected email as an attachment for analysis to samples@virusfree.cz, or re-generate the email and send it directly to this email address.

421 Service temporarily not available

  • You've reached the limit of maximum parallel SMTP connections. Verify the match of IP's PTR record and its hostname as described in RFC 1912 section 2.1 also. You can also verify HERE

Connection timed out

  • You've reached the max connection limit in given time. Please aggregate more into one TCP / SMTP connection if possible.

DNS PTR record point to A record that doesn't point to your IP, see RFC1912


Bulk Senders Guidelines

Identification

Unsubscribe

A user must be able to unsubscribe from your mailing list through one of the following means:

Format

Bulk mail delivery rules