These are the steps to follow when there is an email error:
1. If on Professional then make sure that you are using the external engine in the email settings. If the external engine is not an option you need to upgrade to the latest version. In Professional the settings are under System variables - email settings. In synergy the settings are under Setup - email. Don't get involved in errors on individual mails until you have determined the settings are working correctly by successfully sending a test mail.
2. Go to the email settings. You may not have the full email address in the username field. There is a show password option that can help get the password right. (If it is WILD then it is wrong.)
The settings for gmail are usually easy.
3. If you get a socket error while testing the server, then that means there is no connection to the internet and this is often an AV issue (?? confirm with Joshua). The AV should always be at least paused while testing email settings and in the case of AVast and AVG they are usually best removed completely especially the free versions as they cause problems not only with emails.
4. Usually it is an SMTP error. Errors in the 250's are usually temporary, 220 and 221 are SSL and they have the wrong port or the wrong mode, 500's are usually to do with authentication - often the password is wrong or has been changed, 534 and 535 are gmail authentication errors where either you have 2 step verification on and it must be off or you need to allow access for less secure apps. If it is an own domain eg email adr is fred@ihavemyowndomain.co.za then the mail server is usually (but not always) mail.ihavemyowndomain.co.za and you can try different options on the port and mode settings (open and port 25 always worth a try here). Sometimes own domains are hosted at small third party ISP's which can cause problems in that they may be less stable and the support staff unable to help. If these settings cannot be got working then as a last resort you can set up a gmail account to use and put a forwarder on it to direct any responses to the own domain adr. Sometimes it is better to use the smtp server for the ISP rather than that for the domain. See our list of common SMTP servers for common domains and ISP's eg vodacom, Mweb,etc
5. You can Google the SMTP errors but be aware that the error reporting is not always accurate and that not all servers produce the same error results. Therefore when Googling eg SMTP 534 it is helpful to include the domain / ISP as well.
6. If you cannot get it right with this info then you will need technical help. A competent technician will always be able to resolve the issue. They (techies) can also inspect the smtp log file in case they need to communicate with the service provider or domain host. For Professional this is in C:\mtm2\kudu_etc\emailout.txt. For Synergy it is in C:\Program Files (x86)\MTM\prnum\maillog.txt
6. When sending emails after an email problem, send one at a time until you are sure the problem is resolved after which you can send them 10 at a time. Do not send more than 100 in a day to avoid being blocked as a spammer.
7. If the settings test ok but you still cannot send an individual email it is usually a problem with that individual address. If the test is ok but you cannot send statements then your service provider could be blocking you from including an attachment.
Also see KB article 'How emails work' to understand why your emails may stop working even when you think there have been no changes from your side.