Ian said:
Hi
For some reason I'm not able to receive messages from one particular
contact. I can get email from everyone else.
If a sender receives an email back saying that the message could not be
delivered because of ´501 syntax error ´ is the problem within their system?
Or is the problem within the recipients system?
Thanks for any info.
Ian
Was the error issued by the sender's or recipient's SMTP server? You
getting e-mail doesn't say if the recipient even gets it past their
own SMTp server.
I'll assume the sender is replying to an e-mail that you sent them.
They reply but THEIR server refuses the message. Well, that could be
their fault but it could also be yours. Why yours? Well, YOU are
specifying the From and/or Reply-To headers that they use when they
reply. Those headers tell them to whom they reply. If you have bad
syntax in your From or Reply-To headers then their reply will also use
those bad strings that their SMTP server rejects. So check what YOU
are putting in your From and Reply-To headers.
Also, just because your e-mail complies with the RFCs as to what are
valid characters in the username (left token) of an e-mail address
doesn't mean everyone else's server will accept that syntax. The plus
sign is legit but many servers won't accept it. The pound sign is
legit, too, but some servers (I think Hotmail is like this) won't
allow that character in the left token (left of the ampersand) of an
e-mail address. For example, I use Spamgourmet to create aliases.
E-mails sent to those aliases get delivered to my true e-mail address.
That works fine. Because Spamgourmet is an aliasing service and not
just a forwarding service, they can mask the From and Reply-To headers
to point back to their server. When you reply to an aliased e-mail,
the reply uses their modified From header to send the reply back
through their server which strips out your SMTP's headers, puts the
alias back in the From and Reply-To headers, and even scans the body
of the message to replace the alias with any instance of your true
e-mail address, like in a signature showing contact info. Sounds
great until you find out that Microsoft's parser for their SMTP server
will reject any e-mails with pound signs or other special characters.
Those special characters are valid according to RFCs but Microsoft
decided not to allow them. That means I cannot reply to aliased
e-mails that got delivered to my Hotmail account.
So check what you are putting as your e-mail address in the From and
Reply-To headers in your outbound e-mails. Don't get cutsy and use
characters other than a-z, 0-9, dot, and dash. Using parens, braces,
brackets, dollar signs, quotes, pound, plus, or other characters might
be allowed by your POP3 and SMTP servers but they may not be allowed
at the respondent's SMTP server. I doubt that any e-mail service
provider actually supports the full gamut of characters that the RFCs
state are valid. Sometimes it's not just the characters but how many
pieces or parts there are in the left token. I've seen servers that
permitted (e-mail address removed) for an e-mail address (up to three
parsable parts) but don't allow (e-mail address removed) (where
there are 4, or more, parsable parts). I remember many servers having
problems with Yahoo's aliasing scheme: in a Plus account, you can
define aliases, like (e-mail address removed). Some servers didn't like
the plus sign. Yeah, Yahoo supported the plus character but not all
other servers do.
So look at what you're putting in the From and Reply-To headers in
your outbound e-mails. Make sure there are no spaces in, before, or
after it. Make sure the e-mail address starts with an alphabetic
instead of a number or special character. Limit the use of special
characters to dot, dash, and underscore. Also check the length of
your e-mail address. It's possible it could get truncated if its
dozens of characters in length. Domains usually tend to be under 30
characters in length. Keep your username to under 60 characters in
length and better would be to max out at 30. For example, in the
Spamgourmet aliases that I use, I could use a syntax like
(e-mail address removed). Spamgourmet allows up to 20
characters for each of the various parts in the left token so that
could have a username of 20+1+20+1+20+1+20, or 83, characters in
length. That's damn long and some servers just aren't going to handle
it. They might reject, they might truncate, or do something else
negative that prevents someone from replying to that alias.
Look at what you are telling the other party to use as your e-mail
address when they reply to your e-mail.
