Trouble Sending Email

If your email client seems to be having trouble sending email, please check out the solutions below to errors that may pertain to your issue.

Most common problem

If you are NOT using Acceleration’s DSL or on our network, you may need to change your outgoing SMTP port setting from 25 to 8025. You can generally find this option under Tools » Accounts » More settings » Advanced tab.

Common Sending Errors

If you are receiving any of the following errors, click on the error link below to view the solution to correct the error.

Error “Sender IP must resolve” received when sending mail

The error “5.7.1, Sender IP must resolve” occurs when an email is sent from an IP address that does not have a “reverse DNS lookup” record, also known as a “PTR” record. A PTR record is a way of stating which host name is associated to an IP address. For instance, if we asked which host was associated with “” by using a lookup tool such as “nslookup” within Windows, the result would return “”, which is a Google web server.

With the onslaught of spam, having a PTR record for any and all mail servers is just another step to help others gauge whether or not your server is a valid mail server. Many anti-spam systems will not accept mail from hosts that do not have a PTR record. The best policy is to have a PTR record for any of your hosts visible to the internet, expecially if you run a mail server.

If after contacting your ISP you are unable to attain a PTR record, please contact our support at (800) 655-6505 or email for a bypass rule to be placed into our system.

“We do not relay” error

The “we do not relay” error is received if you try to send an email without previously checking your email within the past 45 minutes. The server will remember who you are when you check your mail for up to 45 minutes, and during that time period, you can send an email. However, if you try to send after that window has expired, the system has purged your IP address and requires you to either check your mail before being permitted to send, or authenticate when sending. This lets your email client send your username and password to the mail server so that it trusts who you are.

To authenticate when sending, here are the steps for various email clients:

On the top menu bar, click “Tools” and then “Email Accounts.” The “View or change existing email accounts” option should be selected by default. If not, please select it. Click “Next.” Select your account by clicking on it once to highlight and then click “Change…” on the right. Click the “More Settings…” button. Click the “Outgoing Server” tab and select “My outgoing server (SMTP) requires authentication.” The “Use same settings as my incoming mail server” option should be checked. If not, select it. Click “OK”, “Next”, and then “Finish.”

Outlook Express:
On the top menu bar, click “Tools” and then “Accounts.” Click the “Mail” tab. Select your account by clicking on it once to highlight it and then click the “Properties” button on the right. Click the “Servers” tab, and then click the box at the bottom that says “My server requires authentication”. Hit “OK” and then “Close”.

On the top menu bar, click “Tools” and then “Account Settings…”. Within the new window, on the left-hand side scroll down and select “Outgoing Server (SMTP)”. On the right-hand side click “Edit…” once the outgoing server has been highlighted. To enable authentication when sending emails, check the checkbox that says “Use name and password”. If not already entered, type in your email address within the “User Name:” field. Once done, click “OK” on both windows to save the settings.

Unable to connect when sending email

If you receive an error when sending email that you are unable to connect, it may be due to your ISP blocking the outbound email. SMTP, the protocol that is used to send email, utilizes port 25 by default. However, ISPs will deny SMTP traffic on this port if it is not destined for one of their mail servers. This is done to reduce the amount of spam that originates from their network due to infected computers. To get around this, Acceleration provides an alternate port, port 8025, which allows for SMTP traffic to reach our mail servers.

Outlook Express:

  1. Click “Tools” on the menu bar, and then select “Accounts”
  2. Double-click on the account you wish to modify under the “Mail” tab
  3. Click the “Advanced” tab
  4. Change 25 to 8025 under “Outgoing mail (SMTP)”


  1. Click “Tools” on the menu bar, and then select “Email Accounts…”
  2. Select “View or change existing email accounts” if not already selected, click “Next >”
  3. Highlight the account you wish to modify and click “Change…”
  4. Click the “More Settings…” button
  5. Click the “Advanced” tab
  6. Change 25 to 8025 under “Outgoing server (SMTP)”


  1. Click “Tools” on the menu bar, and then select “Account Settings…”
  2. In the left pane, scroll down to the “Outgoing Server (SMTP)” area and highlight it
  3. Highlight the outgoing server you wish to modify and then click “Edit…”
  4. Change “Port:” from 25 to 8025

5.7.1 Message cannot be accepted, blacklisted IP address

You receive the following message when attempting to send to a recipient:

5.7.1 Message cannot be accepted, blacklisted IP address.

This message is received due to the IP address of the host attempting to connect to our mail servers being listed on our blacklisted list. If you receive this message in error, please contact us so that we may whitelist the domain or IP address in question.

“Access not allowed” error when sending mail

When sending a message FROM: your domain TO: your domain, such as sending mail from to, you receive a bounce back email stating the following:

Remote host said: 550 5.7.1 Access not allowed

This error occurs due to a mail rule which does not allow for unauthenticated users to send mail FROM: a local system user TO: a local system user, as spammers use this trick to get around filters. In order to be considered authenticated, you must send mail through our mail servers. For instance, if your domain is, your outgoing mail server should be specified as (depending on your ISP, you may need to change the default outgoing SMTP port from 25 to 8025 if you’re unable to connect when sending).

If you wish to not utilize this rule to help reduce the amount of spam you receive, please contact support and request that your domain or single email address be placed on the bypass/opt-out list.

Bounce-back message reports error mentioning “Spamcop”

If you receive a bounce-back message indicating that your message could not be sent due to “Spamcop” this means that the mail server the person you’re trying to email is blocking mail from our mail server because we’re listed on a “Realtime Blackhole List” which lists mail servers that they believe have sent spam. Although our system is not sending out spam by our clients, Auto-Responders (which are used when people go on vacation and such) bounce mail back to addresses that may potentially be “spam traps” which are then used to get mail servers listed on Realtime Blackhole Lists such as Spamcop. Since Auto-Responders are a desired option for people, and spammers will always spam using falsified addresses, the problem will unfortunately always exist. However, we take several measures to make sure that this does not happen that often, and if it does affect you it can usually be resolved by resending your message at a later time, as your message should be resent using a node within our mail cluster that is not listed. You may also elect to send your message through another provider, such as Hotmail or Gmail.

If the above solutions did not solve your issue, contact our support team at 800.655.6505, or use our simple Contact form.